Document and Entity Information - USD ($) $ in Billions	12 Months Ended
	Jan. 31, 2019	Feb. 28, 2019	Jul. 31, 2018
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Jan. 31, 2019
Document Fiscal Year Focus	2019
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 Common Stock, Shares Outstanding		144,332,246
Entity Public Float			$ 3.4
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	false