How to Check Tire Tread Depth with a Penny (and a Quarter)
The penny test is a quick way to check if your tires are too worn to be safe — no gauge required.
Why Tread Depth Matters
Tire tread channels water away from the contact patch, preventing hydroplaning. As tread wears down, wet-road stopping distances increase dramatically. A tire at 2/32" takes 100+ feet more to stop on wet pavement than a new tire.
The Penny Test (Legal Minimum)
Insert a penny into the tread groove with Lincoln's head pointing down into the tire.
- Lincoln's head is covered: You have more than 2/32" — legally OK in most states
- Lincoln's head is fully visible: Tread is at or below 2/32" — replace immediately
The legal minimum in the US is 2/32" (1.6mm). At this depth, tires are dangerously worn for wet conditions.
The Quarter Test (Safety Recommendation)
Insert a quarter with Washington's head pointing down into the groove.
- Washington's head is covered: Tread is above 4/32" — safe for wet roads
- Washington's head is fully visible: Tread is at or below 4/32" — start shopping for replacements
Most tire safety organizations recommend replacement at 4/32", especially if you drive in rain or snow.
Tread Depth Reference Table
| Depth | Coin Test | Status |
|---|---|---|
| 10/32" – 11/32" | — | New tire |
| 6/32" | Quarter: head covered | Good — plenty of life |
| 4/32" | Quarter: head barely visible | Replace soon, especially for wet/snow driving |
| 2/32" | Penny: Lincoln's head visible | At legal limit — replace immediately |
Check Multiple Grooves
Test tread depth in at least 3 spots per tire: inside edge, center, outside edge. Uneven readings indicate an alignment or inflation problem.
Most tires also have tread wear indicators — small raised bars in the grooves that become flush with the surface at 2/32". If you can see these bars, the tire must be replaced.
Frequently Asked Questions
Is the penny test accurate enough?
The penny test is reliable for checking the 2/32' legal minimum. For a safety margin, use the quarter test (4/32') instead — it gives you earlier warning before tires become dangerous in wet conditions.
My tires passed the penny test but I can see the wear indicator bars. Which should I trust?
The wear indicators. They are molded into the tire and are calibrated precisely to 2/32'. If they are flush with the tread, replace the tires regardless of the coin test result.
How do I check for uneven tread wear?
Run your hand across the width of the tread. Uneven wear (one edge lower than the other, or a wavy surface) indicates improper inflation, alignment issues, or worn suspension parts. Get it inspected.
How often should I check tread depth?
Check once a month alongside your tire pressure check. Also check before any road trip. A tread depth gauge costs under $5 and gives a precise reading.