タイヤサイズ計算機

共有リンク

はじめに

Tire Size Calculator — Calculate sidewall height and overall diameter from metric tire size. Enter Section width (mm), Aspect ratio (%), Rim diameter (in) to get an instant, accurate result.

計算式

Sidewall height (mm) = section width × aspect ratio / 100. Overall diameter (in) = (2 × sidewall height / 25.4) + rim diameter (in).

ステップごとの説明

Enter the Section width (mm).
Enter the Aspect ratio (%).
Enter the Rim diameter (in).
Click Calculate to see your result instantly.

実例

Example: With Section width (mm) = 225, Aspect ratio (%) = 45, Rim diameter (in) = 17, the Tire Size Calculator gives Sidewall Height Mm: 101.25, Overall Diameter In: 24.9724.

よくある質問

What do the numbers in a tire size like 225/45R17 mean?

225 is the section width in mm, 45 is the aspect ratio (sidewall height as a % of width), and 17 is the rim diameter in inches.

Why does overall diameter matter when changing tire sizes?

A significantly different overall diameter changes your effective gearing, speedometer accuracy, and ground clearance versus the tire size your vehicle was designed for.

What inputs does the Tire Size Calculator need?

You'll need to provide: Section width (mm), Aspect ratio (%), Rim diameter (in). All fields use sensible defaults, so you can see a working example immediately and then adjust the values to match your own numbers.

How accurate is the Tire Size Calculator?

The Tire Size Calculator applies the formula exactly as calculated — Sidewall height (mm) = section width × aspect ratio / 100. Overall diameter (in) = (2 × sidewall height / 25.4) + rim diameter (in). — so results are precise for the inputs you provide. Accuracy depends on entering correct, realistic input values.

Is the Tire Size Calculator free to use?

Yes, the Tire Size Calculator is completely free, requires no signup, and runs instantly in your browser.