Tires are legally and safely worn out at 2/32" of tread — but you should replace most tires at 4/32" before you lose meaningful wet-weather grip. Here's how to check without any tools and what the numbers mean.
The penny test (2/32" — legally bald)
Insert a penny into the tread groove with Lincoln's head pointing down. If you can see the top of Lincoln's head, your tread is at or below 2/32" — the tire is legally worn out and must be replaced immediately.
At 2/32" the tire has lost most of its ability to evacuate water in wet conditions. Wet stopping distances increase dramatically and hydroplaning risk is very high.
The quarter test (4/32" — recommended replacement)
Insert a quarter with Washington's head pointing down. If you can see the top of Washington's head, tread is at 4/32" or below — replace the tires before winter weather or any significant rain driving.
At 4/32" wet-weather grip has declined noticeably but the tire still handles dry conditions acceptably. Most safety-conscious drivers use 4/32" as their replacement threshold.
Tread wear indicator bars
Modern tires have built-in tread wear indicators — small raised bars molded into the tread grooves at 2/32". When the tire surface is flush with those bars, the tire is at the legal wear limit. No penny needed.
Look for a small triangle or "TWI" marking on the tire sidewall — those point to where the wear indicator bars are in the grooves.
Check tread depth in multiple spots
Check the center of the tread AND both outer edges. Center-only wear = over-inflation. Edge wear = under-inflation or alignment issue. Even if the center looks fine, edge wear means the tire life is compromised.
Also check all four tires. Uneven tread depth across axles can indicate rotation was skipped — and can stress AWD drivetrains if the circumference difference is large enough.
Frequently asked
How often should I check tire tread depth?
Every tire rotation (every 5,000–7,000 miles) is a natural time to check. Also check before a long road trip and before winter.
What's the minimum legal tire tread depth?
2/32" is the minimum legal tread depth in all 50 states. Most safety organizations recommend replacing at 4/32" — especially if you drive in rain.
Can I buy a tread depth gauge?
Yes — they cost $3–10 at any auto parts store and give you a precise reading in 32nds of an inch. More accurate than the penny test for borderline tires.
Last updated 2026-06-27. General guidance only — confirm specifics with a local shop for your exact vehicle.