Tyre Size Calculator UK

Tyre Size Decoder

Enter your tyre size code (e.g. 205/55 R16) to see full dimensions and specifications.

Tyre Size Comparison (Speedometer Check)

Compare your original tyre size with a new size to check speedometer accuracy and clearance suitability.

25 Most Popular UK Tyre Sizes

Load Index & Speed Rating Reference

UK Tyre Safety Laws and Guidance

Tyre safety is one of the most critical aspects of vehicle safety. Your tyres are the only contact point between your car and the road, so ensuring they are in good condition and properly inflated is essential for safe driving. UK law is clear and the penalties for non-compliance are significant.

Legal Minimum Tread Depth: 1.6mm

The Road Vehicles (Construction and Use) Regulations 1986 require that car tyres have a minimum tread depth of 1.6mm across the central three-quarters of the tread width, around the entire circumference of the tyre. Driving on tyres below this limit is a serious offence: you can be fined up to £2,500 per tyre and receive three penalty points on your driving licence. That means a car with all four tyres below the legal limit could face fines of up to £10,000 and 12 penalty points — enough to trigger a totting-up driving ban for some drivers. Additionally, if you are involved in an accident with illegal tyres, your insurance may not pay out.

The legal minimum of 1.6mm is widely considered the absolute minimum, not a safe operating threshold. Major tyre manufacturers and safety organisations including TyreSafe and the RAC recommend replacing tyres at 3mm. Research by MIRA (Motor Industry Research Association) shows that stopping distance on a wet road increases by approximately 44% between 3mm and 1.6mm tread depth at 50mph. Many modern tyres include tread wear indicators (TWIs) moulded into the tyre grooves at 1.6mm — when the tread surface is level with these indicators, the tyre must be replaced.

Tyre Pressure: Why It Matters

Correct tyre pressure is essential for safety, tyre longevity and fuel economy. Under-inflated tyres (below the recommended PSI) flex excessively, causing heat build-up, increased rolling resistance, accelerated tread wear at the outer edges, and reduced fuel economy of up to 3%. Over-inflated tyres have a smaller contact patch with the road, reducing grip particularly in wet conditions, causing premature wear at the centre of the tread, and producing a harsher ride. Tyres naturally lose approximately 1 PSI per month, and cold weather also reduces pressure. Check tyre pressures monthly when cold (before driving more than 2 miles) using a calibrated gauge. The correct pressures for your car are in the handbook and typically on a sticker in the driver's door jamb or fuel filler flap.

Winter vs All-Season vs Summer Tyres in the UK

The UK does not legally require winter tyres, unlike many continental European countries (Germany, Austria, Scandinavian countries). However, winter or all-season tyres provide significant safety benefits in the cold, wet conditions that characterise UK winters from October to March. The key distinction is the 7 degree Celsius threshold: above 7°C, summer compound tyres perform optimally; below 7°C, the harder summer compound begins to stiffen, reducing grip. Winter tyres use softer rubber compounds and deeper, more complex tread patterns including multiple sipes (fine cuts in the tread blocks) that remain flexible in cold temperatures and clear water and slush more effectively. All-season tyres — identifiable by the Three Peak Mountain Snowflake (3PMSF) symbol or the M+S marking on the sidewall — offer a practical compromise for UK drivers who do not want to change tyres seasonally.

Tyre Pressure Monitoring Systems (TPMS)

All new cars sold in the UK and EU since November 2014 are required to be fitted with a Tyre Pressure Monitoring System (TPMS). TPMS warns the driver via a dashboard indicator when tyre pressure drops 25% or more below the recommended level. There are two types: indirect TPMS uses the ABS wheel speed sensors to detect a rolling diameter change caused by pressure loss; direct TPMS uses pressure sensors mounted inside each wheel. If your TPMS warning light illuminates, check all four tyre pressures (and the spare if fitted) immediately. TPMS is tested as part of the MOT inspection for vehicles required to have it fitted — a faulty or missing TPMS unit will result in MOT failure from May 2018 onward.

Budget vs Premium Tyres: The Safety Case

Independent tyre tests conducted annually by TCS Switzerland, Auto Bild, Auto Express and What Car? consistently demonstrate measurable safety differences between budget and premium tyres. In standardised wet braking tests from 50mph, premium tyres from Michelin, Continental, Bridgestone and Pirelli typically stop 5–10 metres shorter than budget alternatives from the same initial speed. At 50mph, 5 metres is a significant distance that could mean the difference between a near-miss and a collision. Budget tyres also tend to wear faster, reducing their overall cost advantage. Mid-range brands including Falken, Hankook, Kumho, Toyo and Nexen offer excellent value — typically within 2–3 metres of premium brands in wet braking tests — at substantially lower prices than the top-tier options.

Frequently Asked Questions