265/70R17 vs 265/65R18
A calculated comparison of tire dimensions, speedometer change and clearance.
Last checked 12 October 2026Published by Sidewall GuideFormulas follow the Tire and Rim Association and ETRTO size conventions
Within 3%: a common safe change
A similar diameter does not confirm fitment. Check load index, wheel width and clearance.
| Dimension | Current | New | Difference |
|---|---|---|---|
| Overall diameter | 31.61 in (803 mm) | 31.56 in (802 mm) | −0.04 in (−0.1%) |
| Section width | 10.43 in (265 mm) | 10.43 in (265 mm) | 0.00 in (0.0%) |
| Sidewall height | 7.30 in (185 mm) | 6.78 in (172 mm) | −0.52 in (−7.1%) |
| Circumference | 99.29 in (2,522 mm) | 99.16 in (2,519 mm) | −0.14 in (−0.1%) |
| Revolutions per mile | 638 | 639 | +1 (+0.1%) |
Your speedometer
When your speedometer reads 30 / 45 / 60 / 75 mph, you are really doing …
| Speedometer reads | You are really doing |
|---|---|
| 30 mph | 30.0 mph |
| 45 mph | 44.9 mph |
| 60 mph | 59.9 mph |
| 75 mph | 74.9 mph |
Your speedometer will read high: you are going slower than it shows.
Your odometer will count 1,000 miles when you have driven 999 miles.
Clearance
Ride height: −0.02 in
Tread edge: no change, on the same wheel offset
Ride height is half the diameter change. The width change splits equally to each side of the tire.
Fitment
Can I fit 265/65R18 instead of 265/70R17?
The calculated overall diameter changes by 0.04 in (0.1%). That is within 3%, a common size-change guideline. This calculation cannot confirm fitment for a specific vehicle.
Plus-sizing
Other sizes near 265/70R17
Common sizes on the same wheel and on +1 and +2 wheels whose overall diameter stays within 3% of 265/70R17's 31.61 in.
Next step
Compare your own sizes
Use the calculator with both sizes prefilled, then change either value to match your vehicle or replacement tire.
Compare your own sizes