Document and Entity Information - USD ($) $ in Billions	12 Months Ended
	Jan. 31, 2018	Feb. 28, 2018	Jul. 31, 2017
Document And Entity Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Jan. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Trading Symbol	BOX
Entity Registrant Name	BOX INC
Entity Central Index Key	0001372612
Current Fiscal Year End Date	--01-31
Entity Filer Category	Large Accelerated Filer
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 2.0
Class A Common Stock
Document And Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		126,152,757
Class B Common Stock
Document And Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		11,357,861