How to read tire tread depth
By Tagwell Auto · Last updated October 10, 2026
The short answer: tread is measured in 32nds of an inch. A new tire has about 10/32. At 4/32, wet grip is fading and it's time to shop. At 2/32 the tire is worn out, and that's the legal minimum in most US states.
Three ways to measure
- A tread depth gauge. A few dollars at any parts store. Push the pin into a main groove, press the base flat and read it. This is the only way to get a real number.
- The penny test. Put a penny in the groove with Lincoln's head down. If you can see all of his head, you're at 2/32 or less. Replace the tire.
- The quarter test. Same idea with Washington's head. If you can see all of it, you're at about 4/32. Start shopping.
Measure in more than one place
Check the inner edge, the middle and the outer edge of each tire, in a few spots around it. A tire is only as good as its most worn groove.
What the numbers mean
| Depth | What to do |
|---|---|
| 6/32 or more | Fine. Keep rotating on schedule |
| 5/32 | Fine in the dry. Wet and snow grip are starting to drop |
| 4/32 | Start shopping. Stopping distances in the rain are noticeably longer |
| 3/32 | Replace soon |
| 2/32 | Worn out. Replace now |
What uneven wear tells you
- Both edges worn: the tire has been run low on air
- The center worn: too much air
- One edge worn: the alignment is out
- Cupping or scallops: worn shocks or struts, or a balance problem
A difference of 2/32 or more between the inner and outer edge is worth an alignment check.
Wear bars
Every tire has small raised bars across the grooves. When the tread is level with them, the tire is at 2/32.
General guidance. Typical intervals, and your owner's manual wins. If a red warning light is on or the car drives differently, stop safely and get help.
Related: Check your tire's age too · Miles and maintenance in Tagwell Auto
Track this automatically in Tagwell Auto
In Tagwell Auto you log tread depth by position. It warns at 4/32 and 2/32, flags uneven wear, and tracks each tire's age from its DOT date.
Questions
What is the minimum legal tread depth?
2/32 of an inch in most US states. Many tire makers suggest replacing sooner, around 4/32, for wet roads.
How do I check tread without a gauge?
Use a penny. With Lincoln's head down in the groove, if you can see all of his head the tread is at 2/32 or less.
Why are my tires wearing unevenly?
Usually air pressure or alignment. Both edges worn means low pressure, the center means too much, and one edge means alignment.