What this site is
Gear Ratio Calculator is a free collection of precision calculators for gear ratios, engine RPM, axle ratios, pulley speeds, speedometer gears, tire-size gearing changes, power-to-weight ratios, and drag-strip ET conversions. Every tool runs entirely in your browser — no sign-up, no downloads.
Why we built it
Most online gear calculators answer one narrow question and stop. We looked at what the best tools across the web each did well — and what they all missed — and combined everything into one place: solve-for-anything inputs, before/after comparisons, buyable gear-set suggestions, metric and imperial units, and plain-English explanations of every result.
How the tools work
Each calculator uses standard automotive and mechanical-engineering formulas (for example, vehicle speed = RPM × tire diameter ÷ (gear ratio × 336.13)). Worked examples on every page show the math step by step, and every page lists its limitations honestly — these are estimates for planning and learning, not a substitute for professional mechanical advice.
Contact
Questions, corrections, or feature requests: contact us here.