Gearbox & RPM Calculator

The drivetrain equation

Road speed = engine RPM ÷ (gear ratio × final drive ratio) × wheel circumference. Short ratios give acceleration; tall ratios give lower cruise RPM and better economy.

• Speed (km/h) = RPM ÷ (r_gear × r_final) × wheel_circumference(m) × 0.06
• A lower final drive (e.g. 4.10 → 3.73) lowers cruise RPM and fuel use, but slows acceleration
• RPM drops when shifting up; the calculator shows speed per gear