Tyre Pressure Calculator
Calculate the correct tyre pressure for your vehicle in PSI, Bar, and kPa
How to Check Your Tyre Pressure
Where to Find Your Vehicle’s Recommended Pressure
Driver’s Door Jamb
Look for a sticker on the inside of the driver’s side door frame. This shows the recommended pressures for front and rear tyres.
Owner’s Manual
Your vehicle handbook contains a complete tyre pressure chart for different load conditions and tyre sizes.
Fuel Filler Cap
Some vehicles display tyre pressure information on the inside of the fuel filler flap or near the petrol cap.
Online Database
Many tyre retailers offer online lookup tools where you can enter your registration number to find the correct pressures.
When to Check Tyre Pressure
Check your tyre pressure when the tyres are **cold** – ideally before driving or at least 3 hours after your last trip. Driving heats up the tyres and increases pressure by 2-4 PSI, giving inaccurate readings.
⚠️ Important Safety Note
Under-inflated tyres are dangerous and illegal. They increase braking distances by up to 11 metres on wet roads and can cause tyre blowouts. Over-inflated tyres reduce the contact patch with the road, affecting grip and causing uneven wear.
Pressure Unit Conversions
UK tyre pressures are commonly expressed in three units: **PSI** (pounds per square inch), **Bar**, and **kPa** (kilopascals). Most UK drivers use PSI, whilst European manufacturers often specify Bar.
2.07 Bar
207 kPa
2.21 Bar
221 kPa
2.41 Bar
241 kPa
2.76 Bar
276 kPa
Quick Conversion Formulas
- **PSI to Bar**: Divide PSI by 14.5
- **Bar to PSI**: Multiply Bar by 14.5
- **PSI to kPa**: Multiply PSI by 6.895
- **kPa to PSI**: Divide kPa by 6.895
Typical UK Vehicle Tyre Pressures
| Vehicle Category | Front Pressure (PSI) | Rear Pressure (PSI) | Notes |
|---|---|---|---|
| Small Cars (Fiesta, Polo) | 30-32 PSI | 28-30 PSI | City driving optimised |
| Medium Cars (Golf, Focus) | 32-35 PSI | 30-33 PSI | Balanced performance |
| Large Cars (Mondeo, Passat) | 34-36 PSI | 32-35 PSI | Motorway stability |
| SUVs/Crossovers | 35-38 PSI | 35-38 PSI | Higher load capacity |
| Vans/Commercial | 40-45 PSI | 42-50 PSI | Varies with load |
These are typical ranges for UK vehicles. Always check your specific vehicle’s requirements as pressures can vary significantly based on tyre size and vehicle specifications.
Effects of Incorrect Tyre Pressure
Under-Inflation Risks
- Increased fuel consumption by up to 3%
- Excessive wear on tyre shoulders
- Higher risk of punctures and blowouts
- Poor handling and longer braking distances
- Increased heat build-up in tyres
Over-Inflation Problems
- Harsh, uncomfortable ride quality
- Centre tread wear pattern
- Reduced grip in wet conditions
- Higher risk of impact damage
- Increased road noise
Legal Requirements in the UK
The UK requires a minimum tread depth of **1.6mm** across the central three-quarters of the tyre. Whilst there’s no specific law about tyre pressure, having significantly under-inflated tyres can be considered dangerous driving, resulting in fines up to **£2,500** and **3 penalty points** per tyre.
Seasonal Pressure Adjustments
Temperature Effects
Tyre pressure changes with temperature – approximately **1 PSI for every 5°C** change. In winter, you may need to add 2-3 PSI to maintain optimal pressure, whilst summer heat can increase pressure beyond recommended levels.
Winter Considerations
Cold weather reduces tyre pressure. Check monthly during winter months and adjust accordingly. Consider winter tyres for temperatures consistently below 7°C.
Summer Precautions
Hot weather and motorway driving can increase tyre pressure. Never reduce pressure when tyres are hot – wait for them to cool down first.
Frequently Asked Questions
How often should I check my tyre pressure?
Check tyre pressure **monthly** and before long journeys. Modern TPMS (Tyre Pressure Monitoring Systems) alert you to significant pressure loss, but regular manual checks are still recommended.
Can I use different pressures for front and rear tyres?
Yes, most vehicles specify different pressures for front and rear tyres. Front tyres often require higher pressure due to engine weight and steering loads.
What’s the difference between normal and full load pressures?
Full load pressures are higher recommendations for when your vehicle is carrying maximum passengers and luggage. This typically adds **2-4 PSI** to the normal pressure recommendations.
Should I include the spare tyre in pressure checks?
Absolutely. Spare tyres should be maintained at the higher of the front or rear pressure recommendations, typically **35-40 PSI** for full-size spares.