How to use this calculator
Enter the loaded mass of the vehicle. Choose percent grade or slope angle and enter the uphill slope. Select speed units and enter a steady speed measured along the inclined road. Read the additional mechanical power required to raise the vehicle against gravity. This is one part of wheel power demand; add separately modeled aerodynamic and rolling loads when studying total road load.
This does not establish towing capacity, traction, cooling ability, gearing, safe climbing speed, braking capacity or a vehicle’s maximum grade. It excludes rolling resistance, air drag, acceleration and powertrain losses. It cannot calculate fuel use from engine displacement, hill angle and speed alone. Uphill slopes only; no descent or regenerative-braking estimate is provided.
The formula
A worked example
For a hypothetical loaded mass of 1,500 kg on a 6% grade at 60 km/h, angle is arctan(0.06) = 3.43 degrees and road speed is 16.6667 m/s. Gravity force is 881.01 N, requiring 14.68 kW (19.69 hp) for climbing alone. At 30 km/h on the same slope the force stays the same while climbing power halves. A 6-degree slope is about 10.51% grade, so it is not interchangeable with 6%.
Climbing power at a fixed slope
Illustrative 1,500 kg loaded mass and 6% grade, with no other loads.
| Road speed (km/h) | Climbing power (kW) |
|---|---|
| 30 | 7.34 |
| 60 | 14.68 |
| 90 | 22.03 |
Common questions
Is a 10% grade a 10-degree hill?
No. Ten percent means 10 units of rise per 100 horizontal units, an angle of about 5.71 degrees. Use the slope selector to match your source. A 100% grade is 45 degrees, not a vertical road.
Why use total mass rather than engine size?
The force due to gravity depends on the mass being lifted and the slope. Displacement alone does not determine either mass or the efficiency and power available at the chosen operating point.
What happens at zero speed or on a level road?
At zero speed the model reports zero climbing power, although a nonzero slope still produces a gravity force. On a level road the climbing force and power are zero. Neither result means that an idling or moving vehicle uses no energy.
Can I include a trailer’s mass?
You can enter combined moving mass to study gravity alone. That does not verify a tow rating, hitch capacity, braking, axle loading or cooling. Trailer air drag and rolling resistance remain excluded.
How much fuel or battery energy will the hill use?
Power is a rate, not an energy quantity. Fuel or battery estimates also need time or elevation gain, other loads and relevant efficiency. This calculator intentionally stops at the mechanical climbing component.
Sources & calculation method
MathWorks: Longitudinal Vehicle includes the gravity term mass × g × sin(angle), distinguishes grade inputs from angles, and treats aerodynamic and rolling resistance separately. This calculator isolates that gravity term and multiplies by road speed. Grade-to-angle conversion follows the rise-over-horizontal-run definition. It uses standard gravity and illustrative inputs rather than manufacturer performance data.
References accessed September 14, 2026. Sources support the stated method, not an endorsement or independent professional review of AutomotiveCalc.
Formula examples and input validation have automated checks. This page has not received an independent automotive professional review. Read our review standards.