Summary Prospectus dated February 1, 2019

as revised November 1, 2019

Calvert Floating-Rate Advantage Fund

Class / Ticker     A / CFOAX     I / CFOIX     R6 / CFORX

This Summary Prospectus is designed to provide investors with key fund information in a clear and concise format. Before you invest, you may want to review the Fund’s Prospectus and Statement of Additional Information, which contain more information about the Fund and its risks. The Fund’s Prospectus and Statement of Additional Information, both dated February 1, 2019, as may be amended or supplemented, are incorporated by reference into this Summary Prospectus. For free paper or electronic copies of the Fund’s Prospectus, Statement of Additional Information, and other information about the Fund, go to http://www.calvert.com/prospectus, email a request to Prospectusrequest@calvert.com, call 1-800-368-2745, or ask any financial advisor, bank, or broker-dealer who offers shares of the Fund. Unless otherwise noted, page number references refer to the current Prospectus for this Fund.

Important Note. Beginning on January 1, 2021, as permitted by regulations adopted by the Securities and Exchange Commission, paper copies of the Fund’s annual and semi-annual shareholder reports will no longer be sent by mail unless you specifically request paper copies of the reports. Instead, the reports will be made available on the Fund’s website (http://www.calvert.com/prospectus), and you will be notified by mail each time a report is posted and provided with a website address to access the report.

If you already elected to receive shareholder reports electronically, you will not be affected by this change and you need not take any action. If you are a direct investor, you may elect to receive shareholder reports and other communications from the Fund electronically by signing up for e-Delivery at calvert.com. If you own your shares through a financial intermediary (such as a broker-dealer or bank), you must contact your financial intermediary to sign up.

You may elect to receive all future Fund shareholder reports in paper free of charge. If you are a direct investor, you can inform the Fund that you wish to continue receiving paper copies of your shareholder reports by calling 1-800-368-2745. If you own these shares through a financial intermediary, you must contact your financial intermediary or follow instructions included with this disclosure, if applicable, to elect to continue to receive paper copies of your shareholder reports. Your election to receive reports in paper will apply to all Calvert funds held directly or to all funds held through your financial intermediary, as applicable.

Investment Objective

The Fund's investment objective is to provide a high level of current income.

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Investors may also pay commissions or other fees to their financial intermediary when they buy and hold shares of the Fund, which are not reflected below. You may qualify for a reduced sales charge on purchases of Class A shares if you invest, or agree to invest over a 13-month period, at least $50,000 in Calvert funds. Certain financial intermediaries also may offer variations in Fund sales charges to their customers as described in Appendix B – Financial Intermediary Sales Charge Variations in the Fund's Prospectus. More information about these and other discounts is available from your financial professional and under “Sales Charges” on page 22 of the Fund's Prospectus and page 19 of the Fund’s Statement of Additional Information.

Shareholder Fees (fees paid directly from your investment)	Class A	Class I	Class R6
Maximum Sales Charge (load) Imposed on Purchases (as a percentage  of offering price)	3.75%	None	None
Maximum Deferred Sales Charge (load) (as a percentage of the lower of net asset value at purchase or redemption)	None	None	None

Annual Fund Operating Expenses (expenses you pay each year as a percentage  of the value of your investment)	Class A	Class I	Class R6
Management Fees(1)	0.71%	0.71%	0.71%
Distribution and Service (12b-1) Fees	0.25%	None	None
Other Expenses(2)	1.24%	1.24%	1.18%
Total Annual Fund Operating  Expenses	2.20%	1.95%	1.89%
Expense Reimbursement(3)	(0.37)%	(0.37)%	(0.37)%
Total Annual Fund Operating Expenses after Expense Reimbursement	1.83%	1.58%	1.52%

⁽¹⁾ Management fees are charged on the Fund’s average daily gross assets and are estimated based on gross assets at the Fund’s most recent fiscal year end.

⁽²⁾ Includes estimated interest expenses and other borrowing costs of 0.81% based on the outstanding borrowings and related costs at the Fund’s most recent fiscal year end.

⁽³⁾ Calvert Research and Management (“CRM”) has agreed to reimburse the Fund’s other expenses (excluding interest expense and other borrowing cost) in excess of 0.06% annually for each class. This expense reimbursement will continue through January 31, 2020. Any amendment to or termination of this reimbursement would require approval of the Board of Trustees. The expense reimbursement relates to ordinary operating expenses only and does not include expenses such as: brokerage commissions, acquired fund fees and expenses of unaffiliated funds, interest expense and other borrowing cost, taxes or litigation expenses. Amounts reimbursed may be recouped by CRM during the same fiscal year to the extent actual expenses are less than the contractual expense cap during such year.

Example. This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, that the operating expenses remain the same and that any reimbursement arrangement remains in place for the contractual period. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

	1 Year	3 Years	5 Years	10 Years
Class A shares	$554	$1,003	$1,478	$2,786
Class I shares	$161	$576	$1,018	$2,245
Class R6 shares	$155	$558	$987	$2,181

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” the portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. For the period from the Fund's inception on October 10, 2017 to September 30, 2018, the Fund's portfolio turnover rate was 35% of the average value of its portfolio.

Principal Investment Strategies

Under normal circumstances, the Fund invests at least 80% of its net assets (plus any borrowings for investment purposes) in income producing floating rate loans and other floating rate debt securities. The Fund invests primarily in senior floating rate loans of domestic and foreign borrowers (“Senior Loans”). Senior Loans typically are secured with specific collateral and have a claim on the assets and/or stock of the borrower that is senior to subordinated debtholders and stockholders of the borrower. Loans usually are of below investment grade quality and have below investment grade credit ratings, which ratings are associated with securities having high risk, speculative characteristics (sometimes referred to as “junk”). The Fund also may borrow from banks for the purpose of acquiring additional income-producing investments (referred to as “leverage”).

The Fund may also invest in secured and unsecured subordinated loans, second lien loans and subordinated bridge loans (“Junior Loans”), other floating rate debt securities, fixed-income debt obligations and money market instruments. Other floating rate debt securities, fixed-income debt securities and money market instruments may include: bonds, notes and debentures issued by corporations; debt securities issued or guaranteed by the U.S. government or one of its agencies or instrumentalities; and commercial paper. Money market instruments with a remaining maturity of less than 60 days are deemed floating rate debt securities. Senior Loans and Junior Loans are referred to together herein as “loans.”

The Fund may invest up to 35% of its net assets in foreign Senior Loans. Foreign Senior Loans must be denominated in U.S. dollars, euros, British pounds, Swiss francs, Canadian dollars, or Australian dollars. The Fund may engage in derivative transactions (such as futures contracts and options thereon, forward foreign currency exchange contracts and other currency hedging strategies, and interest rate swaps) to seek to hedge against fluctuations in currency exchange rates and interest rates. There is no stated limit on the Fund’s use of derivatives.

The Adviser seeks to maintain broad borrower and industry diversification among the Fund’s loans. When selecting loans, the Adviser seeks to implement a systematic risk-weighted approach that utilizes fundamental analysis of risk/return characteristics. Loans may be sold, if in the opinion of the Adviser, the risk-return profile deteriorates or to pursue more attractive investment opportunities. In managing the Fund, the Adviser seeks to invest in a portfolio of loans that it believes will be less volatile over time than the general loan market.

Responsible Investing. In selecting investments for the Fund, CRM is guided by The Calvert Principles for Responsible Investment (a copy of which is included as an appendix to the Fund’s Prospectus), which provide a framework for considering environmental, social and governance (“ESG”) factors.

Calvert Floating-Rate Advantage Fund 2 Summary Prospectus dated February 1, 2019 as revised November 1, 2019

Principal Risks

Market Risk. The value of investments held by the Fund may increase or decrease in response to economic, political and financial events (whether real, expected or perceived) in the U.S. and global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in reaction to changing market conditions. Actions taken by the U.S. Federal Reserve or foreign central banks to stimulate or stabilize economic growth, such as decreases or increases in short-term interest rates, could cause high volatility in markets. No active trading market may exist for certain investments, which may impair the ability of the Fund to sell or to realize the current valuation of such investments in the event of the need to liquidate such assets. Fixed-income markets may experience periods of relatively high volatility in an environment where U.S. treasury yields are rising.

Credit Risk. Investments in loans and other debt obligations (referred to below as “debt instruments”) are subject to the risk of non-payment of scheduled principal and interest. Changes in economic conditions or other circumstances may reduce the capacity of the party obligated to make principal and interest payments on such instruments and may lead to defaults. Such non-payments and defaults may reduce the value of Fund shares and income distributions. The value of debt instruments also may decline because of concerns about the issuer’s ability to make principal and interest payments. In addition, the credit ratings of debt instruments may be lowered if the financial condition of the party obligated to make payments with respect to such instruments deteriorates. In the event of bankruptcy of the issuer of a debt instrument, the Fund could experience delays or limitations with respect to its ability to realize the benefits of any collateral securing the instrument. In order to enforce its rights in the event of a default, bankruptcy or similar situation, the Fund may be required to retain legal or similar counsel, which may increase the Fund’s operating expenses and adversely affect net asset value. Due to their lower place in the borrower’s capital structure, Junior Loans involve a higher degree of overall risk than Senior Loans of the same borrower.

Additional Risks of Loans. Loans are traded in a private, unregulated inter-dealer or inter-bank resale market and are generally subject to contractual restrictions that must be satisfied before a loan can be bought or sold. These restrictions may impede the Fund’s ability to buy or sell loans (thus affecting their liquidity) and may negatively impact the transaction price. See also “Market Risk” above. It also may take longer than seven days for transactions in loans to settle. Due to the possibility of an extended loan settlement process, the Fund may hold cash, sell investments or temporarily borrow from banks or other lenders to meet short-term liquidity needs, such as to satisfy redemption requests from Fund shareholders. The types of covenants included in loan agreements generally vary depending on market conditions, the creditworthiness of the issuer, the nature of the collateral securing the loan and possibly other factors. Loans with fewer covenants that restrict activities of the borrower may provide the borrower with more flexibility to take actions that may be detrimental to the loan holders and provide fewer investor protections in the event of such actions or if covenants are breached. The Fund may experience relatively greater realized or unrealized losses or delays and expense in enforcing its rights with respect to loans with fewer restrictive covenants. Loans to entities located outside of the U.S. may have substantially different lender protections and covenants as compared to loans to U.S. entities and may involve greater risks. Loans may be structured such that they are not securities under securities law, and in the event of fraud or misrepresentation by a borrower, lenders may not have the protection of the anti-fraud provisions of the federal securities laws. Loans are also subject to risks associated with other types of income investments as described herein.

Lower Rated Investments Risk. Investments rated below investment grade and comparable unrated investments (sometimes referred to as “junk”) have speculative characteristics because of the credit risk associated with their issuers. Changes in economic conditions or other circumstances typically have a greater effect on the ability of issuers of lower rated investments to make principal and interest payments than they do on issuers of higher rated investments. An economic downturn generally leads to a higher non-payment rate, and a lower rated investment may lose significant value before a default occurs. Lower rated investments typically are subject to greater price volatility and illiquidity than higher rated investments.

Borrowing Risk. Borrowing cash to increase investments (sometimes referred to as “leverage”) may exaggerate the effect on the Fund’s net asset value of any increase or decrease in the value of the security purchased with the borrowings. Successful use of a borrowing strategy depends on the investment adviser’s ability to predict correctly interest rates and market movements. There can be no assurance that the use of borrowings will be successful. In connection with its borrowings, the Fund will be required to maintain specified asset coverage with respect to such borrowings by applicable federal securities laws and the terms of its credit facility with the lender. The Fund may be required to dispose of portfolio investments on unfavorable terms if market fluctuations or other factors cause the required asset coverage to be less than the prescribed amount. Borrowings involve additional expense to the Fund.

Interest Rate Risk. In general, the value of income securities will fluctuate based on changes in interest rates. The value of these securities is likely to increase when interest rates fall and decline when interest rates rise. Generally, securities with longer maturities are more sensitive to changes in interest rates than shorter maturity securities, causing them to be more volatile. Conversely, fixed income securities with shorter maturities will be less volatile but may provide lower returns than fixed income securities with longer maturities. The impact of interest rate changes is significantly less for

Calvert Floating-Rate Advantage Fund 3 Summary Prospectus dated February 1, 2019 as revised November 1, 2019

floating-rate instruments that have relatively short periodic rate resets (e.g., ninety days or less). In a rising interest rate environment, the duration of income securities that have the ability to be prepaid or called by the issuer may be extended. In a declining interest rate environment, the proceeds from prepaid or maturing instruments may have to be reinvested at a lower interest rate.

Certain instruments held by the Fund pay an interest rate based on the London Interbank Offered Rate (“LIBOR”), which is the average offered rate for various maturities of short-term loans between certain major international banks. LIBOR is expected to be phased out by the end of 2021. While the effect of the phase out cannot yet be determined, it may result in, among other things, increased volatility or illiquidity in markets for instruments based on LIBOR and changes in the value of such instruments.

Foreign Investment Risk. Foreign investments can be adversely affected by political, economic and market developments abroad, including the imposition of economic and other sanctions by the United States or another country. Foreign markets may be smaller, less liquid and more volatile than the major markets in the United States, and as a result, Fund share values may be more volatile. Trading in foreign markets typically involves higher expense than trading in the United States. The Fund may have difficulties enforcing its legal or contractual rights in a foreign country.

Currency Risk. Exchange rates for currencies fluctuate daily. The value of foreign investments may be affected favorably or unfavorably by changes in currency exchange rates in relation to the U.S. dollar. Currency markets generally are not as regulated as securities markets and currency transactions are subject to settlement, custodial and other operational risks.

Money Market Instrument Risk. Money market instruments may be adversely affected by market and economic events, such as a sharp rise in prevailing short-term interest rates; adverse developments in the banking industry, which issues or guarantees many money market instruments; adverse economic, political or other developments affecting issuers of money market instruments; changes in the credit quality of issuers; and default by a counterparty.

U.S. Government Securities Risk. Although certain U.S. Government-sponsored agencies (such as the Federal Home Loan Mortgage Corporation and the Federal National Mortgage Association) may be chartered or sponsored by acts of Congress, their securities are neither issued nor guaranteed by the U.S. Treasury. U.S. Treasury securities generally have a lower return than other obligations because of their higher credit quality and market liquidity.

Derivatives Risk. The Fund’s exposure to derivatives involves risks different from, or possibly greater than, the risks associated with investing directly in securities and other investments. The use of derivatives can lead to losses because of adverse movements in the price or value of the asset, index, rate or instrument underlying a derivative, due to failure of a counterparty or due to tax or regulatory constraints. Derivatives may create leverage in the Fund, which represents a non-cash exposure to the underlying asset, index, rate or instrument. Leverage can increase both the risk and return potential of the Fund. Derivatives risk may be more significant when derivatives are used to enhance return or as a substitute for a cash investment position, rather than solely to hedge the risk of a position held by the Fund. Use of derivatives involves the exercise of specialized skill and judgment, and a transaction may be unsuccessful in whole or in part because of market behavior or unexpected events. Changes in the value of a derivative (including one used for hedging) may not correlate perfectly with the underlying asset, rate, index or instrument. Derivative instruments traded in over-the-counter markets may be difficult to value, may be illiquid, and may be subject to wide swings in valuation caused by changes in the value of the underlying instrument. If a derivative’s counterparty is unable to honor its commitments, the value of Fund shares may decline and the Fund could experience delays in the return of collateral or other assets held by the counterparty. The loss on derivative transactions may substantially exceed the initial investment, particularly when there is no stated limit on the Fund’s use of derivatives. A derivative investment also involves the risks relating to the asset, index, rate or instrument underlying the investment.

Liquidity Risk. The Fund is exposed to liquidity risk when trading volume, lack of a market maker or trading partner, large position size, market conditions, or legal restrictions impair its ability to sell particular investments or to sell them at advantageous market prices. Consequently, the Fund may have to accept a lower price to sell an investment or continue to hold it or keep the position open, sell other investments to raise cash or give up an investment opportunity, any of which could have a negative effect on the Fund’s performance. These effects may be exacerbated during times of financial or political stress.

Risks Associated with Active Management. The success of the Fund’s investment strategy depends on portfolio management’s successful application of analytical skills and investment judgment. Active management involves subjective decisions.

Responsible Investing Risk. Investing primarily in responsible investments carries the risk that, under certain market conditions, the Fund may underperform funds that do not utilize a responsible investment strategy. The application of responsible investment criteria may affect the Fund’s exposure to certain sectors or types of investments, and may impact the Fund’s relative investment performance depending on whether such sectors or investments are in or out of favor in the market. An investment’s ESG performance or the investment adviser's assessment of such performance may change

Calvert Floating-Rate Advantage Fund 4 Summary Prospectus dated February 1, 2019 as revised November 1, 2019

over time, which could cause the Fund to temporarily hold securities that do not comply with the Fund’s responsible investment criteria. In evaluating an investment, the investment adviser is dependent upon information and data that may be incomplete, inaccurate or unavailable, which could adversely affect the analysis of the ESG factors relevant to a particular investment. Successful application of the Fund’s responsible investment strategy will depend on the investment adviser's skill in properly identifying and analyzing material ESG issues.

General Fund Investing Risks. The Fund is not a complete investment program and there is no guarantee that the Fund will achieve its investment objective. It is possible to lose money by investing in the Fund. The Fund is designed to be a long-term investment vehicle and is not suited for short-term trading. Investors in the Fund should have a long-term investment perspective and be able to tolerate potentially sharp declines in value. Purchase and redemption activities by Fund shareholders may impact the management of the Fund and its ability to achieve its investment objective(s). In addition, the redemption by one or more large shareholders or groups of shareholders of their holdings in the Fund could have an adverse impact on the remaining shareholders in the Fund. The Fund relies on various service providers, including the investment adviser, in its operations and is susceptible to operational, information security and related events (such as cyber or hacking attacks) that may affect them or the services that they provide to the Fund. An investment in the Fund is not a deposit in a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

Performance

The following bar chart and table provide some indication of the risks of investing in the Fund by showing how the Fund’s average annual returns over time compare with those of a broad-based securities market index. The return in the bar chart is for Class A shares and does not reflect a sales charge. If the sales charge was reflected, the return would be lower. Past performance (both before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The Fund’s performance reflects the effects of expense reductions. Absent these reductions, performance would have been lower. Updated Fund performance information can be obtained by visiting www.calvert.com.

For the period from December 31, 2017 through December 31, 2018, the highest quarterly total return for Class A was 1.54% for the quarter ended September 30, 2018 and the lowest quarterly return was -4.33% for the quarter ended December 31, 2018.

Average Annual Total Returns as of December 31, 2018	One Year	Life of Fund
Class A  Return Before Taxes	-5.16%	-4.04%
Class A Return After Taxes on Distributions	-6.77%	-5.52%
Class A Return After Taxes on Distributions and Sale of Class A Shares	-3.03%	-3.96%
Class I Return Before Taxes	-1.25%	-0.76%
Class R6 Return Before Taxes	-1.31%	-0.87%
S&P/LSTA Leveraged Loan Index (reflects no deduction for fees, expenses or taxes)	0.44%	1.08%

These returns reflect the maximum sales charge for Class A (3.75%). The Fund commenced operations on October 10, 2017. Investors cannot invest directly in an Index.

After-tax returns are calculated using the highest historical individual federal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on a shareholder’s tax situation and the actual characterization of distributions, and may differ from those shown. After-tax returns are not relevant to shareholders who hold shares in tax-deferred accounts or to shares held by non-taxable entities. After-tax returns for other Classes of shares will vary from the after-tax returns presented for Class A shares. Return After Taxes on Distributions for a period may be the same as Return Before Taxes for that period because no taxable distributions were made during that period. Also, Return After Taxes on Distributions and Sale of Fund Shares for a period may be greater than or equal to Return After Taxes on Distributions for the same period because of losses realized on the sale of Fund shares.

Management

Investment Adviser. Calvert Research and Management (“CRM” or the “Adviser”).

Portfolio Managers

Catherine C. McDermott, Vice President of CRM, has managed the Fund since April 2018.

Craig P. Russ, Vice President of CRM, has managed the Fund since its inception in October 2017.

Calvert Floating-Rate Advantage Fund 5 Summary Prospectus dated February 1, 2019 as revised November 1, 2019

Purchase and Sale of Fund Shares

You may purchase, redeem or exchange Fund shares on any business day, which is any day the New York Stock Exchange is open for business. You may purchase, redeem or exchange Fund shares either through your financial intermediary or directly from the Fund either by writing to the Fund, P.O. Box 219544, Kansas City, MO 64121-9544, or by calling 1-800-368-2745. The minimum initial purchase or exchange into the Fund is $1,000 for Class A, $250,000 for Class I and $1,000,000 for Class R6 (waived in certain circumstances). There is no minimum for subsequent investments.

Tax Information

If your shares are held in a taxable account, the Fund’s distributions will be taxed to you as ordinary income and/or capital gains, unless you are exempt from taxation. If your shares are held in a tax-advantaged account, you will generally be taxed only upon withdrawals from the account.

Payments to Broker-Dealers and Other Financial Intermediaries

If you purchase the Fund’s shares through a broker-dealer or other financial intermediary (such as a bank) (collectively, “financial intermediaries”), the Fund, its principal underwriter and its affiliates may pay the financial intermediary for the sale of Fund shares and related services. These payments may create a conflict of interest by influencing the financial intermediary and your salesperson to recommend the Fund over another investment. Ask your salesperson or visit your financial intermediary’s website for more information.

27382 11.1.19 © 2019 Calvert Research and Management

Calvert Floating-Rate Advantage Fund 6 Summary Prospectus dated February 1, 2019 as revised November 1, 2019