Cover Page - shares	3 Months Ended
	Jun. 24, 2022	Jul. 22, 2022
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 24, 2022
Document Transition Report	false
Entity File Number	001-39675
Entity Registrant Name	ALLEGRO MICROSYSTEMS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	46-2405937
Entity Address, Address Line One	955 Perimeter Road
Entity Address, City or Town	Manchester,
Entity Address, State or Province	NH
Entity Address, Postal Zip Code	03103
City Area Code	603
Local Phone Number	626-2300
Title of 12(b) Security	Common Stock, par value $0.01 per share
Trading Symbol	ALGM
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)		191,269,633
Entity Central Index Key	0000866291
Amendment Flag	false
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--03-31