Tire Tread Depth Calculator
Check all four tire tread depths at once. Get remaining life in km/miles and months, wet stopping distance impact, aquaplaning risk, legal status by region, and coin test guidance — instantly.
A standard passenger car tire starts with 8–10 mm (10–13/32″) of tread. At 6 mm (~7/32″) roughly 70% life remains — still good. Replace at 4/32″ (3 mm) for wet-weather safety. The legal minimum of 2/32″ (1.6 mm) is a fine threshold, not a safety recommendation.
Quick Tread Depth Reference
| Scenario | Pre-computed Answer |
|---|---|
| New tire tread depth | 10/32" (8 mm) — 100% life |
| 7/32" (5.5 mm) | ~70% life remaining — still good |
| 4/32" (3 mm) | ~30% life remaining — consider replacing |
| 2/32" (1.6 mm) | Legal minimum (USA) — replace immediately |
| 6 mm remaining | ~6–7/32" = approximately 60–70% life remaining |
2/32″ is the legal minimum in USA. Replace at 4/32″ for wet weather safety. Winter tires: replace at 4 mm minimum for snow traction.
Overall: Good Condition
Worst tire: Front Left at 6.5 mm
Legal min: 1.6 mm · Replace at: 3 mm
Typical all-season or summer road tire.
Baseline driving behaviour for wear rate estimates.
Remaining (total)
6.5 mm
To legal limit
4.9 mm
Est. km to replace
33600 km
Est. time to replace
1y 10m
🪙 Coin tests pass — Tread depth is adequate
Remaining (total)
6.2 mm
To legal limit
4.6 mm
Est. km to replace
30720 km
Est. time to replace
1y 8m
🪙 Coin tests pass — Tread depth is adequate
Remaining (total)
5.8 mm
To legal limit
4.2 mm
Est. km to replace
26880 km
Est. time to replace
1y 6m
🪙 Coin tests pass — Tread depth is adequate
Remaining (total)
5.6 mm
To legal limit
4.0 mm
Est. km to replace
24960 km
Est. time to replace
1y 5m
🪙 Coin tests pass — Tread depth is adequate
Get a plain-English explanation of your results — what they mean for your vehicle and driving experience.
Tread Depth Status Reference
Pre-calculated status for common real-world scenarios. Standard passenger car tires. Normal driving, EU/UK region.
| Scenario | Depth | 32nds | Status | Est. Time Left | Notes |
|---|---|---|---|---|---|
| Compact Car — New (205/55R16) | 8.0 mm | 10/32" | ✅ New | — | Full tread life remaining |
| Average family car, 1 year old | 6.5 mm | 8.5/32" | ✅ Good | ~24 | Normal wear pattern |
| SUV, 2 years, mixed driving | 5.0 mm | 6.5/32" | ✅ Good | ~18 | Monitor quarterly |
| All-season car, 3–4 years | 4.0 mm | 5/32" | ⚠️ Monitor | ~12 | Wet performance declining |
| Car approaching replacement | 3.0 mm | 4/32" | 🔶 Replace Soon | ~6 | Quarter test: Washington visible |
| Tire at EU replacement recommendation | 3.0 mm | 4/32" | 🔶 Replace | ~4 | +14 m wet stopping at 70 mph |
| Tire at US legal minimum | 1.59 mm | 2/32" | 🚫 Illegal (US) | 0 | Penny test: Lincoln's head visible |
| Tire at EU/UK legal minimum | 1.6 mm | 2/32" | 🚫 Illegal (EU) | 0 | 20p test: outer band visible |
"Est. Time Left" is time to the 3 mm replacement recommendation, assuming normal driving style, mixed roads, and 1,250 km/month. Use the calculator above for personalised estimates.
How to Use This Calculator
- 1
Select your legal region
Choose USA/Canada, EU/UK/Australia, Winter (EU), or Japan. This sets the legal minimum tread depth and replacement warning threshold used in all status badges and estimates.
- 2
Select your tire type
Pick from 8 tire categories: standard summer, performance, touring, winter, all-terrain, EV-reinforced, light truck, or road bicycle. This sets the new-tread benchmark and baseline wear rate for life estimates.
- 3
Set driving style and road surface
Choose your driving style (conservative ×0.75 wear → aggressive ×1.80) and road surface (smooth motorway ×0.85 → full off-road ×2.10). These multiply the base wear rate to match your actual conditions.
- 4
Enter monthly driving distance
Input how many km (or miles) you drive per month. This converts km-to-replacement into calendar months, so you can plan your tire purchase in advance.
- 5
Toggle tire rotation
If you rotate your tires every 8,000–12,000 km, enable the rotation toggle. Regular rotation extends tread life by approximately 15–20% by equalising wear across all four positions.
- 6
Enter current tread depth for each tire
Use the slider or type the current depth for each of the four tires (Front Left, Front Right, Rear Left, Rear Right). Toggle between mm and 32nds of an inch using the units switch. Use the Quick-Set buttons to model scenarios instantly.
- 7
Read results across three tabs
The All Four Tires tab shows status, visual bar, worn %, and coin test per tire. The Wear Analysis tab shows remaining life timeline and wear rate. The Safety Impact tab shows stopping distance delta, aquaplaning risk, and legal/financial exposure.
Coin Test Guide — Penny, Quarter, 20p & Euro
Coin tests are a quick roadside check, but they are not substitutes for a calibrated tread depth gauge. For accurate readings, use a probe-style or digital gauge and measure at three points across the tread width — inner, center, and outer edge.
US Penny
USA / Canada2/32" (1.59 mm)
Insert penny, Lincoln's head down. If you see all of Lincoln's head — tread is at or below 2/32". Replace immediately.
Legal minimum check only — safety threshold is higher.
US Quarter
USA / Canada4/32" (3.18 mm)
Insert quarter, Washington's head down. If you see all of Washington's head — tread is below 4/32". Plan replacement.
Recommended safety threshold. Most experts favour this over the penny test.
UK 20p Coin
UK / EU~1.6 mm
Insert 20p coin upright into main groove. If the outer band is visible — tyre is at or below the 1.6 mm legal limit.
Legal minimum check. TyreSafe-recommended roadside method.
€1 Euro Coin
EU / Eurozone~3 mm
Insert €1 coin into main groove. If the full gold outer rim is clearly visible — tread is below ~3 mm.
Practical replacement warning indicator. Not a legal minimum check.
The Science Behind Tread Depth & Safety
Why tread grooves exist. Tire tread grooves serve one critical function on wet roads: channelling water away from the contact patch fast enough to maintain rubber-to-road contact. At 90 km/h, a tire must displace approximately 8 litres of water per second per millimetre of tread depth. When water cannot be evacuated quickly enough, the tire rides on a water film — aquaplaning — and all steering, braking, and traction control is lost instantly. On dry roads, tread depth matters far less; race cars use slick tires on dry tracks specifically because more rubber contact area increases grip.
The stopping distance cliff below 4 mm. Cardiff University research found that at 113 km/h (70 mph) on wet roads, tires at the 1.6 mm legal limit required up to 27 metres more stopping distance than tires at 4 mm — the equivalent of two car lengths. This is not a gradual decline: wet grip drops sharply below 4 mm as the remaining grooves can no longer displace water fast enough. By the time you reach 1.6 mm, you have already been driving unsafely in rain for some distance above that depth.
Why the legal minimum is not the safety minimum. The 1.6 mm legal minimum was set as a baseline enforcement standard — not as a safety recommendation. Tyre manufacturers, independent safety organisations (TyreSafe, ADAC, NHTSA), and Tire Rack all recommend replacing tires at 3–4 mm for passenger cars and 4–6 mm for winter tires. The gap between "legal" and "safe" is the most dangerous grey zone in everyday motoring — you can pass inspection at 1.6 mm and still have significantly compromised wet-road grip.
Wear rate factors. Tire wear is measured in mm per 10,000 km and is influenced by: tire compound hardness (harder = slower wear, less grip; softer = faster wear, more grip), inflation pressure (under-inflation increases shoulder wear; over-inflation increases centre wear), wheel alignment (camber and toe errors cause diagonal wear patterns), vehicle weight (EVs wear tires 20–30% faster due to battery mass and instant torque delivery), road surface abrasiveness, driving style (hard braking events are the single largest wear accelerator), and rotation frequency (skipped rotations can halve the life of front tires on FWD vehicles).
Reading Tire Wear Patterns — What Uneven Wear Tells You
Centre tread worn, edges normal
Cause: Over-inflation
Action: Reduce pressure to manufacturer's door-placard specification.
Both edges worn, centre normal
Cause: Under-inflation
Action: Inflate to door-placard cold pressure. Check for slow leak.
One edge worn more than the other
Cause: Camber misalignment
Action: Four-wheel alignment check required immediately.
Diagonal / feathering wear pattern
Cause: Toe misalignment
Action: Alignment check. Can cause rapid wear and noise.
Cupping / scalloping (wavy pattern)
Cause: Worn shocks, struts, or suspension bushings
Action: Have suspension inspected. Rotate tires first to confirm.
Front tires wearing much faster than rears
Cause: FWD vehicle — front carries braking + steering loads
Action: Rotate front-to-rear every 8,000–10,000 km.
One tire significantly more worn than its pair
Cause: Misalignment, stuck caliper, or skipped rotation
Action: Check caliper movement, align wheels, begin regular rotation.