Scooter Tire Size Calculator
Read scooter tire codes in mm or inches. Use the calculator below. Results update as you type.
How the Scooter Tire Size Calculator Works
This calculator works by decoding metric scooter sizes such as 120/70-12 and inch sizes such as 3.50-10 into diameter and revs per kilometer. Scooters use small rims from 10 in to 14 in.
- Enter the size, for example 130/70-12.
- Read the diameter: 19.17 in (487 mm).
- Read the width: 5.12 in (130 mm).
- Read the revs per km: 654.
The Formula
The formula uses the metric diameter formula for metric sizes and an estimated 90% sidewall for inch sizes.
Metric: D (mm) = (Rim × 25.4) + 2 × (Width × Aspect ÷ 100) Inch (estimate): D (in) ≈ Rim + 2 × (Inch Width × 0.9) Revs per km = 1,000,000 ÷ (π × D (mm))Worked example: 3.50-10 gives D ≈ 10 + 2 × 3.15 = 16.30 in (414 mm), labeled as an estimate.
Conversion Table
The conversion table lists 11 scooter sizes on 10 in to 14 in rims. Diameters run from 16.30 in (414 mm) to 21.56 in (548 mm).
Small rims turn many times per km. A 10 in scooter tire turns over 730 times per km, close to 1.6 times as often as a car tire.
| Size | Diameter (in) | Diameter (mm) | Width (in) | Revs / km |
|---|---|---|---|---|
| 90/90-10 | 16.38 | 416 | 3.54 | 765 |
| 100/80-10 | 16.30 | 414 | 3.94 | 769 |
| 100/90-10 | 17.09 | 434 | 3.94 | 733 |
| 120/70-12 | 18.61 | 473 | 4.72 | 673 |
| 130/70-12 | 19.17 | 487 | 5.12 | 654 |
| 110/70-13 | 19.06 | 484 | 4.33 | 657 |
| 130/70-13 | 20.17 | 512 | 5.12 | 621 |
| 120/70-14 | 20.61 | 524 | 4.72 | 608 |
| 140/60-14 | 20.61 | 524 | 5.51 | 608 |
| 120/80-14 | 21.56 | 548 | 4.72 | 581 |
| 3.50-10 | 16.30 (est.) | 414 (est.) | 3.50 | 769 |
Inch-coded sizes such as 3.50-10 assume a sidewall near 90% of width (estimate).
What Is the Scooter Tire Size Calculator?
The Scooter Tire Size Calculator is a tool that decodes scooter and moped tire sizes in metric and inch formats. Scooter tires carry small rims and short sidewalls, which make them sensitive to pressure and load.
Many scooters list both a metric and an inch size in the manual. The calculator shows both on the same scale.
Common Uses
This calculator has 4 uses: replacements, size swaps, speedometer checks and tube matching.
- Replace tires: Decode the manual's size.
- Swap sizes: Compare 120/70-12 and 130/70-12.
- Check speedometers: Find the error after a swap.
- Match tubes: Find a tube for inch sizes.