Check if your tyre tread meets the UK legal minimum of 1.6mm
Always have your tyres professionally inspected. Tread depth must meet the legal minimum of 1.6mm across the central three-quarters of the tread width around the entire circumference. Worn tyres significantly increase braking distances, especially in wet conditions.
Tyre tread depth is one of the most critical safety factors on any vehicle, directly affecting grip, braking distance, and aquaplaning resistance. Under UK law (the Road Vehicles (Construction and Use) Regulations 1986), car tyres must have a minimum tread depth of 1.6mm across the central three-quarters of the tread breadth and around the entire circumference. Driving on tyres below this limit is not only dangerous but also a criminal offence carrying severe penalties. This tyre tread depth calculator checks your current tread against the UK legal minimum and estimates how many miles and months of life remain based on your wear history. New tyres typically start with approximately 8mm of tread, and wear gradually through use. The rate of wear depends on driving style, road surfaces, tyre quality, wheel alignment, and tyre pressure. Under-inflated or over-inflated tyres wear unevenly and faster. While 1.6mm is the legal minimum, many safety organisations including the RAC and TyreSafe recommend replacing tyres at 3mm. Research by MIRA (the Motor Industry Research Association) shows that wet braking distances at 50 mph increase by up to 44% when tread drops from 3mm to 1.6mm. In heavy rain, a tyre at the legal limit displaces significantly less water than one at 3mm, dramatically increasing the risk of aquaplaning.
To check your tyre tread status: 1. Enter your current tread depth in millimetres. You can measure this with a tread depth gauge (available from motor factors for a few pounds) or use the 20p coin test as a quick check. If you can see the outer border of the coin when inserted into the tread, it is likely below 3mm and should be professionally measured. 2. Enter the tyre age in months. This is how long since the tyres were fitted, not the manufacturing date. The manufacturing date is shown on the tyre sidewall as a four-digit number (e.g., 2024 means week 20 of 2024), but for wear calculations, the date of fitting is more relevant. 3. Enter your average monthly mileage. If you are unsure, divide your annual mileage by 12. The UK average is approximately 800 miles per month (9,600 miles per year). 4. Review the results. The calculator shows your tread status (Good, Consider replacing, Replace soon, or ILLEGAL), the depth remaining above the legal minimum, estimated months and miles until the legal limit is reached, and the wear rate. If your tyres are below the legal limit, the penalty section shows the fine and points you could face. 5. Check all four tyres individually, as wear can vary between front and rear axles and even between left and right sides. Front tyres on front-wheel-drive cars typically wear faster than rears.
The calculator uses a simple linear wear model based on your tyre history: **Wear rate** = (New tyre depth - Current depth) / Tyre age in months. Assuming new tyres start at 8mm, a tyre that has worn to 3mm in 24 months has a wear rate of (8 - 3) / 24 = 0.21 mm per month. **Months remaining** = (Current depth - Legal minimum) / Wear rate. For a 3mm tyre with a 0.21 mm/month wear rate: (3 - 1.6) / 0.21 = approximately 6.7 months until reaching the legal minimum. **Miles remaining** = Months remaining x Average monthly mileage. At 800 miles per month: 6.7 x 800 = approximately 5,360 miles. **Status thresholds:** 3mm or above = Good (still has significant life). 2-3mm = Consider replacing (wet weather performance is reduced). 1.6-2mm = Replace soon (approaching the legal limit, significantly reduced grip). Below 1.6mm = ILLEGAL (you are committing an offence every time you drive). **Penalty calculation:** Each illegal tyre carries a potential fine of up to GBP 2,500 and 3 penalty points. With four illegal tyres, the maximum penalty is GBP 10,000 and 12 points, which triggers an automatic totting-up disqualification. Additionally, your vehicle will fail its MOT test, and your insurance may be invalidated.