Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 26, 2015	Feb. 12, 2016	Jun. 27, 2015
Document And Entity Information [Abstract]
Entity Registrant Name	NANOMETRICS INC
Entity Central Index Key	0000704532
Document Type	10-K
Document Period End Date	Dec. 26, 2015
Amendment Flag	false
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	FY
Trading Symbol	NANO
Current Fiscal Year End Date	--12-26
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		24,297,590
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 400.6