The penny test tells you if your tires are worn down enough to need replacing
The penny test is a quick way to check whether your tire tread has worn down to the point where you should replace the tire. You place a penny into the tread grooves of your tire with Lincoln's head upside down and facing into the groove. If you can see the top of Lincoln's head, your tread is too shallow and the tire needs to be replaced. If the tread covers part of Lincoln's head, your tire still has adequate tread.
This test works because the distance from the edge of a penny to the top of Lincoln's head is about 2/32 of an inch — the legal minimum tread depth in most U.S. states. When tread wears down to that point, your tires lose grip in wet conditions and are more likely to hydroplane. The penny test does not replace a professional inspection, but it gives you a reliable snapshot of whether replacement is urgent.
Key Takeaways
- Insert a penny into your tire tread with Lincoln's head facing downward and away from you.
- If you can see the top of Lincoln's head, your tread depth is at or below the legal minimum and replacement is needed soon.
- If the tread covers part of Lincoln's head, you have adequate tread depth for now.
- Test multiple spots around each tire, since wear is often uneven across the surface.
- The penny test is a screening tool, not a substitute for professional tire inspection or balance checks.
Where to insert the penny and how to position it
Hold the penny between your thumb and forefinger so that Lincoln's head faces downward. Find a groove in the tire tread — the channels that run around the tire. Insert the penny into the groove with Lincoln's head pointing away from you, so the top of his head goes into the tread first.
Push the penny down into the groove as far as it will go. The penny should sit snugly in the groove without forcing. If the groove is very shallow, the penny may not fit deeply at all, which itself is a sign that tread is low.
Reading the results: what you are looking for
Once the penny is seated in the groove, look at whether the top of Lincoln's head is visible. If you can see the very top of his head above the tread, your tread depth is at or below 2/32 of an inch. This is the legal minimum in most states, and it means your tires should be replaced soon — do not wait.
If the tread covers the top of Lincoln's head so that you cannot see it, your tread depth is above 2/32 of an inch and your tire is still legal. However, many tire professionals recommend replacing tires at 4/32 of an inch, which is before the legal minimum. At that depth, wet traction begins to drop noticeably. You can test for 4/32 depth using a quarter instead of a penny: if you can see the top of Washington's head on a quarter, you are at or below 4/32.
Test multiple locations on each tire
Tire wear is often uneven. The outer edges may wear faster than the center, or one side of the tire may wear more than the other. Test at least three or four spots around each tire — near the outer edge, in the middle, and on the other outer edge — to get a full picture of how the tire is wearing.
If some spots show good tread and others show worn tread, the tire is still at risk. Uneven wear can signal alignment problems, underinflation, or suspension issues that a mechanic should inspect. Even if the deepest grooves still pass the penny test, uneven wear is worth mentioning at your next service.
What uneven wear patterns can tell you
If the outer edges of your tires are wearing much faster than the center, your tires may be underinflated or your vehicle's wheels may be out of alignment. If the center of the tire is wearing faster, overinflation or aggressive driving may be the cause. If one tire is wearing much faster than the others, a brake caliper may be sticking or your alignment may be off on that side.
The penny test only measures depth, not the reason for wear. If you notice a pattern, mention it to a mechanic or tire shop. They can check your alignment, tire pressure, and suspension to prevent premature wear on your next set of tires.
When to replace tires beyond what the penny test shows
The penny test tells you about tread depth, but tires can need replacement for other reasons. If you see cracks in the sidewall, bulges, or objects embedded in the tread, the tire should be replaced even if tread depth is adequate. Tires also have an age limit: most manufacturers recommend replacement after six to ten years, regardless of tread depth, because the rubber hardens over time.
If your vehicle pulls to one side, vibrates, or makes noise while driving, have the tires and wheels inspected by a professional. These symptoms can point to alignment, balance, or structural problems that the penny test cannot detect. A tire shop can also measure tread depth with a gauge, which is more precise than the penny method.
Frequently Asked Questions
Can I use a different coin instead of a penny?
A penny works because the distance to the top of Lincoln's head is about 2/32 of an inch. A dime or nickel will not give you the same measurement. If you want to test for 4/32 depth instead, a quarter works: Washington's head sits at about 4/32 of an inch from the edge.
What if the penny fits so loosely that it falls out?
If the penny falls out or sits very loosely in the groove, your tread is extremely shallow and replacement is urgent. Tread that shallow means very little grip, especially in rain or snow. Do not delay on replacing the tire.
Do I need to check all four tires?
Yes. All four tires wear at different rates depending on your vehicle's weight distribution, driving habits, and road conditions. Check each tire at multiple spots. If any tire fails the penny test, it should be replaced.
Is the penny test accurate enough to rely on completely?
The penny test is a useful screening tool, but a tire gauge gives a more precise measurement. If you are unsure after the penny test, a tire shop can measure depth with a gauge for a few dollars or for free. A professional inspection also checks for damage, alignment issues, and age that the penny test does not reveal.
What should I do if my tires pass the penny test but feel like they are slipping?
Slipping can happen even with adequate tread depth if your tires are underinflated, misaligned, or damaged in ways the penny test does not show. Check your tire pressure against the recommended PSI on your driver's door jamb. If pressure is correct and slipping continues, have a mechanic inspect the tires, brakes, and suspension.