Work out gear ratio for vehicle instantly with clear inputs, formula shown and shareable results.
Road speed is engine rpm divided by the overall ratio (gearbox times final drive), times tyre circumference. Speed per 1000 rpm in top gear is the single most useful gearing figure: 35-45 km/h is typical for a relaxed motorway cruiser.
Gearing
wheel rpm = engine rpm / (gear ratio x final drive); speed = wheel rpm x circumference x 60 / 1e6
One giving 35-45 km/h per 1000 rpm, so 100 km/h sits at 2,200-2,800 rpm — near peak efficiency without losing all flexibility.
A shorter final drive improves acceleration at the cost of cruising rpm and economy. It is the cheapest way to alter the whole gearing set.