Tyre Size Calculator
Find and verify the correct tyre size specification for your vehicle — enter width, aspect ratio and rim diameter to get the standard code instantly.
Tyre Size Specification Calculator
Find and verify the exact tyre specification format.
What is the Tyre Size Calculator?
The Tyre Size Calculator helps you decode and verify the three-part tyre size code printed on the sidewall of any tyre. By entering the tyre width in millimetres, the aspect ratio (sidewall height as a percentage of width), and the rim diameter in inches, the tool instantly generates the standardised tyre size designation used globally — for example 205/55 R16.
Fitting the wrong tyre size can affect speedometer accuracy, handling, ground clearance, and fuel efficiency. Use this tool to confirm specifications before purchasing replacement tyres.
Why use our Tyre Size Calculator?
Instant Size Code Generation
Combines width, aspect ratio and rim size into the standardised international tyre designation in real time as you type.
Prevents Incorrect Fitment
Verifying size before purchase prevents the common and costly mistake of buying tyres that do not fit your wheels or meet your vehicle's load/speed rating.
Works for Cars, SUVs & Bikes
The standard tyre size format is used across all vehicle categories. Enter the correct values for any vehicle type and get the right size code.
Fully Mobile-Friendly
Access the calculator from your phone while standing in front of a tyre rack — get the right code before the sales person quotes you the wrong size.
Sidewall Code Explained
Use the generated code to cross-reference with your vehicle owner's manual or manufacturer door sticker to confirm you are choosing the correct replacement.
No Registration Needed
Open the tool and use it immediately. No account, no tracking, no cost. Your inputs stay in your browser only.
Find your tyre size in 3 steps
Enter the Tyre Width
Find the width in millimetres from your current tyre sidewall (e.g. 205 in 205/55 R16) or from your vehicle's owner manual. Enter this number in the Width field.
Set the Aspect Ratio
The aspect ratio is the two-digit number after the slash (e.g. 55 in 205/55 R16). It represents the sidewall height as a percentage of the tyre width.
Enter the Rim Diameter
Enter the wheel/rim size in inches (e.g. 16 in 205/55 R16). The result will show the complete standardised tyre size code you should use when purchasing replacement tyres.
Frequently Asked Questions
Look at the sidewall of any of your current tyres. The size is printed in a format like 205/55 R16. You can also find the manufacturer-recommended size on the sticker inside the driver's door jamb or in the owner's manual.
Sometimes yes, within limits. A slightly wider or narrower tyre may fit, but it can affect speedometer accuracy, fuel economy, handling, and ground clearance. Always consult a professional tyre fitter before deviating from the original specification.
The "R" stands for Radial construction — the type of internal tyre construction where the cords run perpendicular to the direction of travel. Virtually all modern passenger car tyres are radial-construction.
Absolutely. Tyre rim diameter must exactly match your wheel rim size. A tyre labelled R16 will only fit on a 16-inch rim. Mismatching will make the tyre impossible to mount safely.
Extra letters indicate load index or usage category — XL means Extra Load (reinforced sidewall for heavier vehicles), and C means Commercial. These are separate from the size code and should also be matched when replacing.
Explore More Automotive Tools
Each tool is purpose-built for real automotive decisions — all free, all instant.
Fuel Cost Calculator
Estimate your trip fuel expense instantly with real mileage parameters and pump prices.
Open ToolCar EMI Calculator
Compute your exact monthly car loan installment with reducing-balance amortization clarity.
Open ToolMaintenance Scheduler
Personalized upkeep schedule tailored to your current odometer reading and vehicle type.
Open ToolEngine Oil Capacity
Suggested crankcase oil capacity and filter requirements by vehicle engine displacement format.
Open Tool