How to Use the Tire Tread Wear Calculator
Tire tread grooves grip the road and channel water away for braking and drainage. Most U.S. states require replacement once tread depth reaches 2/32 inch, and it's a common failure point in state safety inspections. Enter your new tire's tread depth, current depth, and miles driven since they were new, and this calculator shows how much tread you've worn per 10,000 miles and, assuming that rate continues, how many miles remain before hitting the legal limit.
As tread approaches 2/32 inch, wet-road drainage performance drops sharply, raising the risk of hydroplaning and significantly increasing stopping distances. While 2/32 inch is the legal minimum in most states, many tire experts recommend replacing sooner - around 4/32 inch - for a real safety margin.
The classic penny test (insert a penny with Lincoln's head down; if you can see all of it, you're near the limit) is a quick way to check, but for a precise reading, use a tire tread depth gauge and pair it with this calculator's mileage estimate.
Frequently Asked Questions
Most U.S. states require tires to be replaced once tread depth reaches 2/32 inch, and it's the failure point in most state vehicle inspections. Below this depth, wet-road drainage drops sharply and stopping distances get much longer.
The classic penny test - insert a penny with Lincoln's head down into the tread groove - shows you're near the 2/32 inch limit if you can see all of his head. For an exact reading, use a tire tread depth gauge.
It's not illegal, but there's almost no safety margin left. Hydroplaning risk rises sharply in wet weather, which is why many tire experts recommend replacing at 4/32 inch instead of waiting for the legal minimum.