Tread Depth Calculator

Wear bars sit at 2/32". How you get there depends on how fast you have been using tread.

Example: started at 10/32", now 6/32", 20,000 miles on them → about 5,000 miles per 32nd, ~20,000 miles to the bars.

Tread depth and wear bars
10/32"2/32"tread surface
  • Depth is measured in 32nds of an inch, from the groove floor up to the tread surface.
  • A new highway tire starts around 10/32". The wear bar is moulded inside the groove at 2/32".
  • When the tread wears flush with the bar, 2/32" is left and the tire has reached the end of its service life.
  • Federal rules require tires to carry those bars. The limit for driving is set by each state; in Florida it is 2/32".

What it does

Projects remaining miles with a linear wear model: miles already used ÷ tread already used × tread left down to 2/32".

How to use it

Enter current depth (in 32nds or inches), miles on the tire, and optional monthly miles. Original depth defaults to 10/32" for a typical passenger tire unless you override it.

How to read the result

FMVSS 139 requires wear-bar indicators that become flush at 2/32". That is a federal construction rule, not a nationwide ban on driving. Most US states prohibit passenger tires worn past those bars. Wet braking falls off well before 2/32" — many shops recommend replacing around 4/32" for rain.

What this does not calculate

Wear is not perfectly linear. Alignment, rotation, inflation, climate and compound change the rate. If you just rotated, the rate from the first 5,000 miles may not match the next 5,000.

Does not inspect for uneven wear, cupping, or belt damage. A tire can be unsafe with tread left.

Questions

Is 2/32" the federal legal minimum to drive?
No. Federal rules require the wear bars. Whether you may drive below 2/32" is state law. Do not treat this as legal advice.
Should I replace at 4/32" instead?
For heavy rain, yes, many safety groups recommend it. This calculator still aims at the wear-bar height and tells you when you are already low.

Related tools

Estimate — not a fitment approval.

Tread Depth Calculator