Document and Entity Information	9 Months Ended
	Sep. 28, 2013	Nov. 04, 2013
Document and Entity Information [Abstract]
Entity Registrant Name	NANOMETRICS INC
Entity Central Index Key	0000704532
Document Type	10-Q
Document Period End Date	Sep. 28, 2013
Amendment Flag	false
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-28
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		23,349,469