Rolling Resistance Calculator
Rolling Resistance Results
What Is a Rolling Resistance Calculator?
A Rolling Resistance Calculator is a tool that estimates the force created when a wheel rolls across a surface. This calculator uses vehicle mass, the coefficient of rolling resistance, and speed to estimate rolling resistance force, power demand, normal force, and an equivalent road incline.
A rolling resistance calculator helps you estimate how much force and power are needed to keep a vehicle moving at a steady speed. Enter vehicle mass, choose or enter a rolling resistance coefficient, and add speed. The tool returns force in newtons and pounds-force, plus power in watts, horsepower, and kilowatts.
The result is not a full vehicle performance model. It focuses only on rolling resistance. It does not include aerodynamic drag, acceleration, drivetrain loss, braking, tire temperature changes, road slope beyond the equivalent grade display, or wind. That makes it a focused tool for understanding one part of vehicle motion.
How the Rolling Resistance Formula Works
The calculator first converts the entered vehicle mass into kilograms if needed. It then calculates normal force using standard gravity. Normal force is the force from the vehicle’s weight pressing down on the surface.
In these formulas, m is vehicle mass in kilograms, g is 9.80665 m/s², FN is normal force in newtons, Crr is the coefficient of rolling resistance, Fr is rolling resistance force in newtons, v is speed in meters per second, and P is power in watts.
The calculator also converts force from newtons to pounds-force using 1 N = 0.224809 lbf. Power is shown in watts, horsepower, and kilowatts. It uses 1 W = 0.00134102 hp and 1 W = 0.001 kW. The equivalent incline is calculated as Crr × 100, shown as a percent grade.
Example: suppose the vehicle mass is 1,500 kg, Crr is 0.015, and speed is 60 km/h. The normal force is 1,500 × 9.80665 = 14,709.98 N. The rolling resistance force is 0.015 × 14,709.98 = 220.65 N, or 49.6 lbf. The speed is 60 ÷ 3.6 = 16.67 m/s. Power is 220.65 × 16.67 = 3,677.49 W, or 4.93 hp and 3.68 kW. The equivalent incline is 0.015 × 100 = 1.5%.
The calculator accepts zero speed, which makes power equal to zero because power depends on speed. It also accepts a Crr value of zero, which makes rolling resistance force equal to zero. It hides results if mass is missing or not positive, if Crr is missing or negative, or if speed is missing or negative.
How to Use the Rolling Resistance Calculator: Step by Step
- Enter the Vehicle Mass. Use the mass of the vehicle or object you want to evaluate.
- Select the Mass Unit. Choose kilograms or pounds.
- Enter the Coefficient of Rolling Resistance (Crr), or choose a surface from the quick select menu.
- Use Quick Select Surface if you want a preset Crr value, such as car tire on asphalt, rolled gravel, sand, or bicycle tire on smooth tarmac.
- Enter the Speed. This is the speed used to calculate the power needed to overcome rolling resistance.
- Select the Speed Unit. The calculator supports km/h, mph, and m/s.
- Click Calculate Resistance to view the result, or click Reset to clear all fields.
The output shows rolling resistance force, power to overcome that force, normal force, equivalent incline, and a plain-English summary. Read the force result as the steady push needed to keep the vehicle rolling on the chosen surface, before adding other real-world loads like air resistance or hills.
What Your Rolling Resistance Calculator Result Means
The rolling resistance force tells you how hard the surface and tire combination resists motion. A heavier vehicle creates more normal force, so it creates more rolling resistance when Crr stays the same. A higher Crr also raises the force, even if the vehicle mass does not change.
Surface selection matters
The quick select menu fills the Crr input with preset values. These include steel wheel on steel rail, truck tire on concrete, car tire on concrete, car tire on asphalt, rough asphalt, rolled gravel, tarmacadam, soft grass, sand, bicycle tire on smooth tarmac, and bicycle tire on rough road. You can also use a custom value.
| Quick Select Surface | Crr Used by Calculator |
|---|---|
| Steel Wheel on Steel Rail | 0.006 |
| Truck Tire on Concrete | 0.01 |
| Car Tire on Concrete | 0.013 |
| Car Tire on Asphalt | 0.015 |
| Car Tire on Rough Asphalt | 0.02 |
| Rolled Gravel | 0.025 |
| Tarmacadam | 0.05 |
| Soft Grass | 0.1 |
| Sand | 0.3 |
| Bicycle Tire on Smooth Tarmac | 0.004 |
| Bicycle Tire on Rough Road | 0.008 |
Power depends on speed
Rolling resistance force does not change with speed in this calculator. Power does. The tool multiplies force by speed in meters per second, so a higher speed means more watts, horsepower, and kilowatts are needed to overcome the same rolling resistance force.
The incline result is an equivalent grade
The equivalent incline compares the rolling resistance coefficient to a constant uphill grade. For example, a Crr of 0.015 is shown as a 1.5% grade. This is a simple comparison from the calculator formula, not a full hill-climbing model.
Results are estimates for reference use. Real rolling resistance can change with tire pressure, tire wear, temperature, tire construction, road texture, vehicle load, and surface condition. For critical design, testing, racing, or engineering decisions, confirm Crr values with manufacturer data or measured results.
Frequently Asked Questions
What is rolling resistance?
Rolling resistance is the force that opposes a wheel as it rolls across a surface. In this calculator, it is found by multiplying the coefficient of rolling resistance by the normal force. A larger vehicle mass or higher Crr creates a larger rolling resistance force.
How do I calculate rolling resistance force?
To calculate rolling resistance force, multiply normal force by the coefficient of rolling resistance. This calculator first finds normal force from mass and gravity, then applies the selected or entered Crr value. It displays the result in newtons and pounds-force.
What is Crr in a rolling resistance calculator?
Crr means coefficient of rolling resistance. It is a decimal value that represents how much a surface and wheel combination resists rolling. This calculator lets you enter Crr manually or pick a preset value from the surface menu, such as car tire on asphalt or sand.
Why does speed affect power but not rolling resistance force?
Speed affects power because the calculator uses power = force × speed. The rolling resistance force comes from Crr multiplied by normal force, so speed is not part of that force formula. As speed rises, the same force requires more watts to overcome.
Is rolling resistance the same as aerodynamic drag?
No, rolling resistance is not the same as aerodynamic drag. Rolling resistance comes from the wheel and surface interaction. Aerodynamic drag comes from moving through air. This calculator only estimates rolling resistance, normal force, power for rolling resistance, and an equivalent incline.
How accurate is this rolling resistance calculator?
This rolling resistance calculator is as accurate as the mass, speed, and Crr value you enter. It uses fixed unit conversions and standard gravity. Real results can vary because Crr changes with tire pressure, temperature, tire wear, surface condition, and manufacturer-specific tire data.
What does equivalent uphill grade mean?
Equivalent uphill grade shows Crr as a percent grade by multiplying Crr by 100. For example, Crr 0.02 appears as a 2% uphill grade. It is a plain comparison to help users understand the effect of rolling resistance, not a full slope or traction calculation.