✦ Compare tyre sizesStep 1 of 2
Compare the tyres you have against a size you're thinking about. See how the overall diameter, sidewall, ride height and revs change — and how far your speedometer would be out, since it's calibrated to the original size.
205/55R16 to 225/45R17
+0.4%
diameter vs your current tyre (+2.4 mm)
New diameter
634 mm
24.97 in
Ride height
+1.2 mm
at the axle
Speedo at 60 mph
60.2
mph actual
Within spec
Under the ±3% rule most fitment guides use — speedo and gearing barely change.
Current tyre
205/55R16Width
mm
Profile
%
Rim
in
Popular sizes
New tyre
225/45R17Width
mm
Profile
%
Rim
in
Side by side, to scale
Current — 205/55R16New — 225/45R17
Both tyres drawn sitting on the same road. The gap at the top is how much taller (or shorter) the new tyre stands.
The numbers
| Current | New | Change | |
|---|---|---|---|
| Overall diameter | 631.9 mm | 634.3 mm | +2.4 mm |
| Diameter (inches) | 24.88 in | 24.97 in | +0.09 in |
| Sidewall height | 112.8 mm | 101.3 mm | -11.5 mm |
| Section width | 205 mm | 225 mm | +20 mm |
| Circumference | 1.985 m | 1.993 m | +0.8 cm |
| Revolutions / mile | 811 | 808 | -3 |
| True speed at 60 mph indicated | 60 mph | 60.2 mph | +0.2 mph |
A planning estimate from the size numbers alone — real rolling diameter varies a little by tyre model, load, pressure and wear, and actual fit depends on your wheel offset, guard clearance and any speed-rating or load-index requirements. The ±3% guideline is a rule of thumb, not a legal limit; check your owner's manual and local rules. Everything runs in your browser.
Pairs well with
About Tyre Size Calculator
Compare two tyre sizes and see exactly what changes. Enter your current size and a new one (width / profile / rim) to get the overall diameter, sidewall height, circumference, revs per km or mile, ride-height change and the speedometer error the swap introduces — with a to-scale side-by-side diagram and a ±3% fit verdict. Works for plus-sizing, going taller for clearance, or just checking a set you found cheap.
Everything happens on your device. Close the tab and it's gone.