Tire Size Calculator
Parse WWW/AARRR sizes into diameter and compare speedometer error. Click any i for detail.
Tire sizes
Tire size
i
Size
Format like 225/45R17. |
|
|---|---|
Compare size (optional)
i
Alt
Second size for diameter delta / speedo sketch. |
How to use this calculator
- Enter a size like 225/45R17.
- Optionally enter a second size to compare.
- Read sidewall, diameter, and circumference.
- Use speedo % only as a rough change estimate.
Results explained
Metric tire codes encode section width, aspect ratio, and rim diameter. Sidewall mm = width × aspect/100; overall diameter inches = rim + 2×(sidewall/25.4). Speedometer error sketches compare diameters.
Quick reference: tire geometry
sidewall_mm = width×(aspect/100); D_in = rim + 2×(sidewall/25.4).
| Item | Detail |
|---|---|
| 225/45R17 | Common performance size |
| Wider/shorter | Often similar diameter |
| Speedo % | (D2−D1)/D1 × 100 |
| Load/speed ratings | Not decoded here |
Confirm fitment, load rating, and clearance before buying.
How the estimate is built
D = rim + 2×(width×aspect/100)/25.4; speedo% = (D2−D1)/D1×100.
Example scenario
225/45R17 diameter is about 25.0 in (see live result for exact).
FAQ
Plus-sizing?
Compare diameters carefully — keep overall height close.
LT or Flotation sizes?
This parser expects metric WWW/AARRR.
Circumference use?
Useful for revs/mile sketches.
TPMS / clearance?
Check vehicle specs — not modeled.