Tire Size Calculator
Enter tire size in standard format: Width / Aspect Ratio / Rim (e.g. 205/55/R16)
Compare Second Tire Size
Please enter valid tire dimensions.
How to Read a Tire Size Code
Every tire has a size code moulded into its sidewall, such as 205/55 R16. Understanding what these numbers mean helps you choose the right replacement tires and understand how a size change affects your vehicle.
- 205 – Section width in millimetres (the widest point of the inflated tire).
- 55 – Aspect ratio: the sidewall height as a percentage of the section width. Here, 55% of 205mm = 112.75mm sidewall.
- R16 – Radial construction, 16-inch rim diameter.
Why Tire Diameter Matters
Changing tire size affects your speedometer reading, odometer accuracy, ground clearance, and gearing. If the overall diameter changes by more than 3%, you may need to recalibrate your speedometer or adjust your gear ratios.
Frequently Asked Questions
Can I fit a wider tire without changing the rim?
Generally yes, within limits. Most rims can accommodate tires 10–20mm wider than the original. Check your vehicle's wheel arch clearance and the rim's approved width range.
How does aspect ratio affect ride quality?
A higher aspect ratio (taller sidewall) gives a softer, more comfortable ride and better pothole absorption. A lower aspect ratio (sportier profile) improves cornering response but transmits more road harshness.
What does "R" mean in tire size?
"R" stands for Radial construction — the dominant tire type today. Radial tires have ply cords arranged radially (perpendicular to the direction of travel), providing better fuel efficiency and longevity than older bias-ply tires.
Will changing tire size affect fuel economy?
Yes. A larger diameter means more revolutions per kilometre, slightly increasing rotational mass and rolling resistance. The effect is typically small (1–3%) but noticeable over long distances.