Tyre Size Calculator

Use our tyre size calculator to compare tyre sizes and see exactly how a change will affect your vehicle. Instantly view differences in overall diameter, rolling circumference, sidewall height and speedometer accuracy - key factors when considering alternative tyre sizes.

Compare tyre sizes

To find your Original Equipment (OE) tyre sizes.
Current size
Size 2
Size 3
Size 4
Measurements
Tyre type

Disclaimer: Results are indicative only. Tyre dimensions and rolling diameter can vary between brands, models and tread patterns, even where the listed size is the same.

Frequently Asked Questions

What is a tyre size calculator?
A tyre size calculator compares different tyre sizes and shows changes in diameter, rolling circumference, width and speedometer accuracy.
What is plus sizing?
Plus sizing means increasing wheel diameter while reducing tyre sidewall height to maintain similar overall rolling diameter.
How much can I change tyre size legally in Australia?
Most Australian states allow a maximum overall diameter increase of 25mm for passenger vehicles and 50mm for 4WD vehicles, but regulations vary. Always check local laws.
Will changing tyre size affect my speedometer?
Yes, changing tyre size can affect your speedometer accuracy. A larger tyre will cause your speedometer to read slower than your actual speed, while a smaller tyre will cause it to read faster. A safe approach is to keep changes within 2-3% of the original tyre size to minimise speedometer error.
Is wider always better?
Wider tyres can provide better grip and handling, but they also increase rolling resistance and can reduce fuel efficiency. Consider your driving needs and vehicle specifications when choosing tyre width.