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Tire Tread Wear Calculator: How Many Miles Are Left

Comparing how much tread you've lost against how far you've driven gives a reasonable estimate of how many miles you have left before replacement.

Tread depth is measured in 32nds of an inch (or mm)

A new passenger tire typically starts around 10/32 to 11/32 inch (about 8 mm) of tread depth. In the US, tread depth is usually described in 32nds of an inch; elsewhere it is measured in millimeters.

Wear rate = tread lost Γ· miles driven

Subtract current tread depth from original tread depth, then divide by the miles driven so far. This gives you a wear rate in 32nds of an inch (or mm) per mile.

Remaining miles = tread left above the legal minimum Γ· wear rate

Subtract the legal minimum tread depth (commonly 2/32 inch, about 1.6 mm) from your current tread depth, then divide by your wear rate to estimate how many more miles the tire has before it needs replacing.

Built-in wear bars offer a quick visual check

Nearly all modern tires have small raised bars molded into the tread grooves that become flush with the tread surface at 2/32 inch β€” if the tread is level with these bars, the tire has reached the legal minimum regardless of any calculation.

The penny test is a rough substitute for measuring

Insert a penny into a tread groove with Lincoln's head upside down and facing you; if you can see all of his head, tread depth is at or below about 2/32 inch and the tire needs replacing.

Why tread wear rate is not perfectly linear

Front and rear tires often wear at different rates depending on drivetrain and alignment, and wear accelerates somewhat as tread gets shallower because less rubber volume is left to absorb the same driving forces. Treat a mileage estimate as a useful planning figure, not an exact countdown.

Tread depth affects safety well before hitting the legal minimum

Wet-weather stopping distance and hydroplaning resistance both degrade noticeably as tread shallows, even above the legal minimum β€” many safety organizations recommend considering replacement around 4/32 inch for tires that see regular wet-weather driving, rather than waiting for the legal floor.

Frequently Asked Questions

Is 2/32 inch tread depth actually safe to drive on?

It's legal in most US states, but performance in rain or snow is noticeably worse than a tire with more tread. Many drivers replace tires closer to 4/32 inch, especially before a wet or winter season.

Do all four tires wear at the same rate?

Usually not. Front-wheel-drive vehicles tend to wear front tires faster; alignment issues, tire rotation habits, and driving style all affect the rate differently per tire, so measuring each tire individually gives a more accurate picture than assuming uniform wear.