Document and Entity Information	9 Months Ended
	Sep. 27, 2014	Oct. 24, 2014
Document and Entity Information [Abstract]
Entity Registrant Name	NANOMETRICS INC
Entity Central Index Key	0000704532
Document Type	10-Q
Document Period End Date	Sep. 27, 2014
Amendment Flag	false
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-27
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		24,158,015