Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2021	May 04, 2021
Cover [Abstract]
Entity Registrant Name	ACME UNITED CORP
Entity Central Index Key	0000002098
Document Type	10-Q
Document Period End Date	Mar. 31, 2021
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		3,483,527
Document Fiscal Period Focus	Q1
Document Fiscal Year Focus	2021
Trading Symbol	ACU
Entity Emerging Growth Company	false
Entity Small Business	true
Entity Shell Company	false
Entity File Number	01-07698
Entity Tax Identification Number	06-0236700
Entity Address, Address Line One	1 Waterview Drive
Entity Address, City or Town	Shelton
Entity Address, State or Province	CT
Entity Address, Postal Zip Code	06484
City Area Code	203
Local Phone Number	254-6060
Entity Interactive Data Current	Yes
Title of 12(b) Security	$2.50 par value Common Stock
Security Exchange Name	NYSEAMER
Entity Incorporation, State or Country Code	CT
Document Quarterly Report	true
Document Transition Report	false