Tire Size Calculator
Compare tire sizes, check diameter and speedometer impact, and convert metric to inches with this free tire size calculator in your browser.
Tyre size
Accepts metric (265/70R17, 265 70 17, LT285/75R16) and flotation (33x12.50R15) — tyre or tire spelling. Runs in your browser.
Results
- Overall diameter
- 802.8 mm (31.61 in)
- Section width
- 265.0 mm (10.43 in)
- Sidewall height
- 185.5 mm (7.30 in)
- Circumference
- 2.52 m (99.3 in)
- Revs per km
- 396
- Revs per mile
- 638
- Flotation estimate
- ≈ 31.5x10.43R17
A 265/70R17 tyre stands about 803 mm (31.61 in) tall and 265 mm wide, turning about 396 times per kilometre.
Estimates only — check before you fit
These results are calculated from tyre-size geometry and the values you enter. Real tyre dimensions vary by brand, model, load, pressure and wear. Always check the vehicle placard, tyre manufacturer data, local road rules, and guard / brake / suspension clearance, and get professional fitment advice before changing tyre or wheel sizes.
How to use this calculator
- Type a tyre size in almost any format — 265/70R17, 265 70 17, LT285/75R16 or flotation like 33x12.50R15.
- Or tap one of the example sizes.
- Read the overall diameter, width, sidewall, circumference and revolutions per km/mile, and switch mm-first or inch-first display.
How it works
Sidewall height = section width × aspect ratio ÷ 100. Overall diameter = rim + 2 × sidewall. Circumference = diameter × π, and revolutions per km = 1,000,000 ÷ circumference in mm (per mile = 63,360 ÷ circumference in inches).
Flotation sizes (33x12.50R15) state the overall diameter and width in inches directly, so the tool works back to an equivalent metric width and aspect. The diagram is drawn to scale from these numbers — it's original line-art, not a photo.
Worked example
265/70R17. Overall diameter ≈ 31.61 in (802.8 mm), section width ≈ 10.43 in, sidewall ≈ 7.30 in, about 396 revolutions per km — a common 4WD size.
Frequently asked questions
What do the numbers in 265/70R17 mean?
265 is the section width in mm, 70 is the aspect ratio (sidewall height as a percentage of width), R means radial, and 17 is the rim diameter in inches.
What is a flotation size like 33x12.50R15?
It states the values in inches: 33 in overall diameter, 12.50 in wide, on a 15 in rim. Common on 4WDs. The tool converts it to an equivalent metric width and aspect for comparison.
Why does revolutions per km matter?
It drives speedometer and odometer accuracy. A taller tyre turns fewer times per km, so the speedo reads low. Use the Speedometer Error Calculator to see the effect.
Are these results safe to fit?
They're geometry estimates only. Real tyres vary by brand, load, pressure and wear. Always check the vehicle placard, manufacturer data, local road rules and guard/brake/suspension clearance, and get professional fitment advice before changing tyre or wheel sizes.
Related tools
- Speedometer Error Calculator
- Tire Size Comparison Visualizer
- Alternate Tire Size Finder
- Tire Size Chart by Diameter
- Tire Size Chart by Wheel Size
- 4WD Tyre Clearance Change Calculator
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Cite this tool
Zerdly. (2026). Tire Size Calculator. Retrieved from https://www.zerdly.com/tools/tire-size-calculator/
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.