DRIVETRAIN PLANNING

Semi Truck Gear Ratio & Engine RPM Calculator

Estimate engine RPM at a selected road speed using explicit axle, top-gear and loaded tire-revolution inputs.

Change the assumptions to explore a scenario. Results update immediately.

Road speed (km/h)Rear axle ratioTop transmission gear ratioLoaded tire revolutions per kilometre

Estimated engine RPM at selected road speed2,044 RPM

Loaded tire radius, tire wear, exact gearing, drivetrain slip and operating conditions can change observed RPM. No single RPM is universally optimal.

Rear axle ratio guide Transmission research Truck spec planner

Method, example & interpretation

Method: Estimated RPM equals road speed in km/h × loaded tire revolutions per kilometre × axle ratio × top-gear ratio ÷ 60.

Worked example: 100 km/h × 500 rev/km × 3.00 axle × 0.75 top gear ÷ 60 equals 1,875 RPM.

Interpretation: Compare the result with the exact engine, transmission, axle and loaded-tire documentation. It is not a gearing or engineering recommendation.

Blank, invalid and negative entries are treated conservatively as zero or the minimum valid term. Displayed defaults are illustrative scenarios, not current market facts.