Tyre Tread Depth Checker
Check each tyre against the 1.6mm legal minimum for cars, and see which ones are getting close.
How does the tyre tread depth checker work?
Enter a tread depth reading in millimetres for each of your four tyres. The checker compares each one with the 1.6mm legal minimum for cars and labels it Illegal (below 1.6mm), Legal but marginal (1.6mm to just under 2mm), Fine, monitor (2mm to just under 3mm) or Good (3mm or more). The overall result follows your worst tyre, because one tyre below the limit is enough to make the car non-compliant.
Only the 1.6mm figure is the law. The 2mm and 3mm bands are this site's own guide, based on the common advice to think about replacing tyres around 3mm.
3 worked examples
Example 1 — All four tyres well above the limit
Readings: 4.2mm, 4.0mm, 3.8mm, 3.9mm.
All four are "Good": every reading is above 3mm, well over the 1.6mm minimum.
Example 2 — One tyre in the marginal band
Readings: 3.5mm, 3.4mm, 1.8mm, 3.6mm. The rear left is close to the limit.
All four are legal, because 1.8mm is above 1.6mm, but the rear left is flagged as marginal. Many tyre advisers suggest replacing before the legal limit rather than waiting for it, so it is worth planning a replacement soon.
Example 3 — One illegal tyre
Readings: 3.0mm, 2.8mm, 1.4mm, 2.9mm. The rear left is below the minimum.
The overall result is illegal, even though the other three are fine. The tyre should be replaced before the car is driven on the road. Penalties are set per illegal tyre; see the next sections.
Example 3 shows why all four tyres need checking, not just the ones that look worn. Wear is not always even between the front and the back.
The legal minimum tread depth explained
GOV.UK's safety guidance says each tyre should have a tread depth of at least 1.6mm, checked across the central three-quarters of the breadth of the tread and around the entire circumference. This checker is for cars. Other vehicles, such as motorcycles and larger vehicles, have different tread requirements, so check GOV.UK for those.
| Tread depth | Status in this checker | Guidance |
|---|---|---|
| 3mm and above | Good | Comfortably above the minimum |
| 2mm to under 3mm | Fine, monitor | Legal, but into the range where many advisers suggest planning a replacement |
| 1.6mm to under 2mm | Legal but marginal | Meets the minimum, but with very little margin left |
| Below 1.6mm | Illegal | Below the legal minimum; replace before driving |
Penalties for illegal tyres
The RAC reports the penalty as applying per illegal tyre:
- Up to a £2,500 fine and 3 penalty points for each illegal tyre. The RAC puts the maximum at £10,000 in fines if all four tyres are illegal. Twelve points in theory could add up to a driving ban, but the penalties set by a court depend on the case, and these are maximums, not typical outcomes.
- MOT failure. Goodyear's guide to the MOT rules says a primary groove below 1.6mm fails.
- Possible insurance problems. I haven't found an official statement on this, so check your policy wording.
Use our Penalty Points Calculator to see how points add up.
Why tread depth matters
Tread helps the tyre push water out from under it, so worn tyres tend to grip less well on a wet road and may be more prone to aquaplaning. This is the reason tyre bodies often recommend replacing before the legal limit: the RAC says most recommend replacing at around 3mm.
I haven't quoted a figure for how much longer stopping takes at a given tread depth, because the results of tyre tests vary by tyre, vehicle and test conditions. "Legal" doesn't mean "performs like a new tyre". Our Stopping Distance Calculator shows how distances grow with speed and on wet roads, but it has no tyre setting.
How to measure your own tread depth
- The 20p test. Put a 20p coin into the main tread grooves. The RAC says that if you can't see the coin's outer band, the tyre is above the legal limit. If the band is visible, the tyre could be unsafe and should be inspected professionally.
- A tread depth gauge. Inexpensive, and gives a reading in millimetres rather than a rough pass or fail.
- Check several points. Measure the inner, middle and outer parts of the central three-quarters, and at more than one place around the tyre, because wear is often uneven. Uneven wear can point to a pressure or alignment problem.
What this checker can't tell you
Uneven wear
The tool takes one figure per tyre. If tread varies across the width or around the tyre, a single reading can miss a part that is already below the limit.
Other tyre faults
Goodyear's MOT guide lists other reasons a tyre can fail, including deep cuts that expose the cords or ply, bulges or tears in the sidewall, mismatched tyre types on the same axle and a faulty tyre pressure warning system. This checker only looks at tread.
When to replace
A "marginal" or "fine, monitor" result is a guide, not a verdict. How soon to replace also depends on your mileage and the journeys ahead, such as a long wet-weather motorway trip.
Common mistakes
Only checking the tyres that look worn
Check all four. A tyre you rarely look at, such as a rear one, can be the worst.
Measuring only one spot
A tyre can read well in one place and be much lower in another. Take readings at several points.
Treating an MOT pass as a long-term guarantee
An MOT only records the condition on the day. A tyre that passes with little tread left may wear below the limit before the next test, so keep checking.
How we calculate
Per tyre: below 1.6mm = Illegal · 1.6mm to under 2.0mm = Legal but marginal · 2.0mm to under 3.0mm = Fine, monitor · 3.0mm or more = Good. A reading of exactly 1.6mm counts as legal. Only the 1.6mm limit is from the law; the other thresholds are this site's own guide.
Overall result follows the worst single tyre: if any tyre is illegal, the overall result is illegal.
🚗 See your full annual running costs
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Use the Running Cost Calculator →Frequently asked questions
What is the legal minimum tyre tread depth in the UK?
For cars it is 1.6mm, across the central three-quarters of the breadth of the tread and around the entire circumference of the tyre, according to GOV.UK.
What happens if I'm caught driving on illegal tyres?
According to the RAC, up to a £2,500 fine and 3 penalty points per illegal tyre. These are maximums. A tyre below the legal tread depth also fails the MOT.
How do I check my tyre tread depth without a gauge?
Use the 20p test. Put the coin in the main grooves: if the coin's outer band is hidden, the tread is above the legal limit, and if the band shows, have the tyre checked. A gauge gives a more exact reading.
Should I wait until 1.6mm to replace a tyre?
Not necessarily. The RAC says most advisers recommend replacing around 3mm, because grip, especially in the wet, tends to fall as tread wears. The legal limit is a minimum, not a target.
Do all four tyres need to be above the legal minimum?
Yes. Each tyre is judged on its own, so three good tyres don't make up for a fourth below 1.6mm.
References & data sources
- GOV.UK — Tow a trailer or caravan with a car: safety checks. States the 1.6mm minimum, checked across the central three-quarters of the breadth of the tread and around the entire circumference. GOV.UK's dedicated tyre page could not be loaded when I checked, so confirm the car rules there as well.
- RAC — Checking tyre tread. Per-tyre penalties (up to £2,500 and 3 points), the 20p test and the common advice to replace at around 3mm. A motoring organisation's guidance, not the law itself.
- Goodyear — MOT tyre rules. MOT tread and other tyre failure points. A tyre maker's summary, so check the DVSA MOT inspection manual for the official wording.
This checker assesses only the tread figures you enter. It cannot replace a physical inspection of all four tyres for uneven wear, cuts, bulges or other faults.
Prakash
Prakash is the founder and editor of UK Driving Tools. He maintains the site's calculators and guides and checks the rates and rules they use against official UK sources, such as GOV.UK, the DVLA, HMRC and Transport for London, before publishing.
Pages are drafted with the help of AI tools and then checked by the editor. He isn't a lawyer, accountant or UK-qualified adviser, so every page lists its sources and states what its calculator can't tell you. Nothing on this site is legal or financial advice.
Pages on UK Driving Tools are drafted with the help of AI tools. Before publishing, the figures and rules on each page are checked against the official source named on the page, and calculator examples are tested against the working formula. Pages are updated when rates or rules change. Our Editorial Policy explains the full process, including how to report a mistake.
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