Pick a calculator
Choose by task; browse all if you are unsure.
01 · TOOLS
All Calculators
01
Tire Size Calculator
Enter tire width, aspect ratio and rim diameter to estimate sidewall height, overall diameter, circumference and revolutions per mile.
免费 · Free02
Tire Size Comparison
Compare two tire sizes by overall diameter, diameter difference, speedometer error and radius change.
免费 · Free03
Wheel Offset Calculator
Convert wheel width and offset into backspacing and front spacing.
免费 · Free02 · HOW
How to use
Enter dimensions
Units sit next to each input; results convert automatically.
Read result and assumptions
Waste allowance is included; verify before ordering.
03 · WHY
Why use this site
01
Verifiable math
Every page shows the formula, assumptions and margin. No black box.
02
No signup
Open and calculate. Inputs stay in your browser and are not uploaded.
03
Localized
Chinese and English switch automatically, with units and rules adapted per market.
04 · FAQ
FAQ
How accurate is this?
Estimates follow public formulas with stated assumptions; verify high-stakes decisions on site.
Is it free?
All calculators are free today. Any future Pro tier will be priced on the page.
Do you store my inputs?
No. The math runs locally in your browser and is never submitted.