Tire Size Calculator
Decode tire spec numbers into diameter, sidewall, circumference, and revs/mile — and compare two sizes before you buy.
Sidewall height as % of width
Overall diameter (mm)
634
Breakdown
- Tire 1
- 225/45R17
- Diameter (in)
- 24.97
- Sidewall height (mm)
- 101
- Circumference (mm)
- 1,993
- Revolutions per mile
- 808
- Tire 2 (comparison)
- 245/40R18
- Diameter 2 (mm)
- 653
- Diameter difference
- 2.98%
- Verdict
- Within ±3% — speedometer stays accurate
Last updated:
FAQ
What does 225/45R17 mean?
225 mm section width, sidewall equal to 45% of that (about 101 mm), R for radial construction, mounting on a 17-inch rim. Overall diameter is the rim plus two sidewalls — roughly 634 mm here.
How much can I change tire size?
Keep the overall diameter within about ±3% to avoid speedometer error, odometer drift, and ABS calibration issues. Wider tires may also rub fenders at full steering lock — check clearances first.
Do plus-size wheels affect fuel economy?
Usually slightly worse. Larger rims add rotating mass and often wider, grippier rubber, both raising rolling resistance. Expect a few percent worse economy versus the stock setup.
Related Calculators
Tip Calculator
→Calculate the tip amount and total bill per person, with smart service-quality presets and rounding options.
Split the Bill Calculator
→Split a bill fairly between friends, with optional tip and separate handling of shared vs personal items.
GPA Calculator
→Calculate your grade point average on a 4.0 scale from course grades and credit hours, with cumulative GPA support.
Grade Calculator
→Find what you need on the final exam to reach your target course grade, based on current grade and exam weight.