The minimum tire tread depth acceptable by law is

The minimum tire tread depth acceptable by law is 2/32 of an inch.

In most U.S. states, the legal minimum tire tread depth is 2/32 of an inch (about 1.6 mm). However, it’s worth noting that many tire safety experts recommend replacing tires before they get that worn down – typically when they reach 4/32 inch, especially if you drive in rainy conditions.

At 2/32 inch, tires have significantly reduced ability to channel water away, which increases the risk of hydroplaning.

A simple way to check your tread depth is the penny test: insert a penny into the tread with Lincoln’s head upside down. If you can see the top of Lincoln’s head, your tread is at or below 2/32 inch and it’s time for new tires.