Penny Test for Tires: How to Check Tread Depth

Last updated November 9, 2026

To do the penny test, put a penny into a tire groove with Lincoln’s head upside down. If you can see the top of his head, the tread is at 2/32 of an inch or less. That means it is time for new tires.

Checking tread takes two minutes and could prevent a crash on wet or snowy roads. This guide explains the penny test, the built-in wear bars, tread gauges and other signs your tires need replacing.

Key Takeaways

• The National Highway Traffic Safety Administration says to replace tires at 2/32 of an inch of tread.
• If you see the top of Lincoln’s head in the penny test, replace the tires.
• Raised wear bars between the grooves show when tread is too low.
• Check tread and tire pressure at least once a month.
• Some makers suggest replacing tires after 6 to 10 years, even with good tread.

Inside this guide

1. Why tread depth matters
2. How to do the penny test
3. Check the wear bars
4. Use a tread depth gauge
5. Signs of uneven wear
6. How old are your tires?
7. Tread for winter driving
8. Make tires last longer
9. Frequently asked questions

Why Tread Depth Matters

Tread grooves push water, slush and snow away from the tire. That keeps the rubber in contact with the road.

As tread wears down, the tire grips less, especially in rain. Worn tires take longer to stop and are more likely to hydroplane.

The highway safety agency reports that 511 people died in tire-related crashes in 2024. Its tire safety page urges drivers to check their tires every month.

How to Do the Penny Test

The penny test is a quick, free way to check tread at home. All you need is a single penny.

1. Park on a flat surface and turn off the engine.
2. Hold a penny with Lincoln’s head pointing down into the tire.
3. Push the penny into one of the main grooves.
4. Look at how much of Lincoln’s head you can see.
5. Repeat in several spots across each tire, including the inner and outer grooves.

What the result means

Check more than one spot. Tires often wear unevenly, so one groove may pass while another fails.

Check the Built-In Wear Bars

Every tire has small raised bars inside the grooves. Their proper name is treadwear indicators.

When the tread wears down level with these bars, the tire has reached the replacement point. The agency says to replace the tires at that stage.

Look for small arrows or marks on the tire shoulder. They often point to where the wear bars sit.

Use a Tread Depth Gauge

A tread depth gauge gives an exact reading. It costs only a few dollars at auto parts stores.

1. Push the gauge pin into a main groove until the base sits flat on the tread.
2. Read the number, usually shown in 32nds of an inch.
3. Check the inner, center and outer grooves on each tire.
4. Write down the readings so you can track wear over time.

The table shows common rules of thumb. Your tire maker and local laws may have their own guidance.

Signs of Uneven Wear

How a tire wears can point to other car problems. Look at the whole tread, not just one spot.

• Worn center only, which often means too much air pressure
• Worn on both edges, which often means too little air pressure
• Worn on one edge, which can point to an alignment problem
• Patchy or cupped wear, which can mean worn suspension parts
• Bulges, cracks or cuts in the sidewall, which need attention right away

If you see uneven wear, ask a mechanic to check alignment, balance and suspension. Fixing the cause protects your new tires.

How Old Are Your Tires?

Rubber ages even when tires sit unused. Old tires can crack and fail even with deep tread.

The agency notes that some vehicle makers recommend replacing tires that are 6 to 10 years old, regardless of tread. Check your owner’s manual for your car’s advice.

How to find the date

Look for the Tire Identification Number on the sidewall. The last four digits show the week and year of manufacture.

For example, 0308 means the third week of 2008. A tire with that code is far too old to trust, whatever its tread looks like.

Tread for Winter Driving

Snow and slush need deeper tread than dry roads. Tires near the 2/32 limit can feel fine in summer but slide badly in winter.

If your tread is close to 4/32 before winter, consider replacing the tires early. Dedicated winter tires offer the best grip in cold, icy weather.

Before the snow arrives, read our guide on how to drive in snow. Keep a set of jumper cables handy too, and learn how to jump-start a car.

Make Your Tires Last Longer

Keep them properly inflated

Check tire pressure at least monthly when the tires are cold. Use the number on the label inside the driver’s door or in the manual. Do not use the number printed on the tire.

The agency says properly inflated tires can save up to 11 cents per gallon of fuel. They can also add about 4,700 miles to tire life.

Yet only 19 percent of drivers keep their tires properly inflated, according to the same page.

Rotate them

If your car maker recommends it, rotate tires every 5,000 to 8,000 miles. Rotation helps all four tires wear evenly.

Watch your warning lights

The tire pressure light comes on only when a tire is very low. It does not replace monthly checks, as our guide to dashboard warning lights explains.

Cold mornings also lower tire pressure. Learn why in our guide to tire pressure in cold weather.

Check for Tire Recalls

Makers sometimes recall tires for safety defects. You can search for tire recalls on the highway safety agency’s website using the tire’s identification number.

Register new tires with the maker when you buy them. That way, the maker can tell you if a recall affects your set.

Penny Test vs Other Tread Checks

Use the penny test monthly and ask for a professional check at each oil change. Together they catch most tire problems early.

When to Replace Tires

• Lincoln’s whole head shows in the penny test
• The tread is level with the wear bars
• A gauge reads 2/32 of an inch or less
• The sidewall has bulges, deep cracks or cuts
• The tires are older than your maker recommends

Replace tires in pairs or full sets when possible. Matching tires help the car handle evenly.

Your Tire Check Checklist

• I did the penny test in several grooves
• I checked the wear bars
• I looked for uneven wear and sidewall damage
• I found the tire age on the sidewall
• I checked the tire pressure when cold
• I searched for tire recalls

Add tire checks to your monthly routine with our car maintenance checklist. Heading out on a winter road trip? Use our winter packing list too.

Test Yourself

Frequently Asked Questions

Is the penny test accurate?

It is a good quick check for the 2/32 limit. A tread gauge gives a more exact reading.

How long do tires usually last?

It depends on driving, care and tire type. Check tread monthly and watch the tire age.

Should I replace all four tires at once?

It is best for handling, especially on all-wheel-drive cars. At minimum, replace tires in pairs.

Does tire tread matter for electric cars?

Yes. Electric cars are heavy and quick, which can wear tires faster, so check them often.

Conclusion

The penny test is the fastest way to know if your tires are safe. If you see the top of Lincoln’s head, replace them.

Check tread and pressure monthly, look for uneven wear and keep an eye on tire age.

Editor’s Note

This guide is accurate as of November 9, 2026. It draws on tire safety guidance from the National Highway Traffic Safety Administration.

Always follow your vehicle and tire maker’s advice, and ask a trusted mechanic if you are unsure.

Spot an error in this article? Please contact us at support@digieh.com or read our Corrections Policy.

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