Calculating rolling resistance was difficult... until we created this rolling resistance calculator! You don't need to do all the science and research to know how to calculate rolling resistance — we did it all for you. Here you can figure out whether you should buy those fancy low rolling resistance tires to save gas in your car or to improve your cycling wattage output.
Rolling resistance — basics
People usually don't understand rolling resistance well, but everyone seems to have an idea of what it means. It has to do with your wheels when you're driving. Generally, you want the least rolling resistance possible, and you can reduce it if you buy low rolling resistance tires. Some of you might even know that rolling resistance is a type of friction force that slows you down.
All of that is correct, but we are here to help you go deeper. Did you know that rolling resistance doesn't depend on your tire size, but it does depend on the weight of your car, bike, or train? The best way to explain it is to learn the physics behind it. The easiest way is just to use this rolling resistance calculator to check how each factor affects, for example, the bike tire rolling resistance.
Tire rolling resistance
We often mention rolling resistance in relation to tires in vehicles. That's because the tire's contact with the road, and the way they react to each other, is what causes rolling resistance. Changing the tires is the easiest, cheapest, and fastest way to change the rolling resistance of your car or bike.
Nowadays, you can even buy low rolling resistance tires that help minimize the energy lost to the road when driving around. These are generally more expensive and don't make economical sense for the average user. However, in performance applications, the difference between a regular tire and a low rolling resistance tire can mean the difference between first and last.
But don't let this confuse you — rolling resistance is not something inherent to tires only. Anytime you have an object rolling on top of a surface, you get rolling resistance.
What is rolling resistance caused by?
Rolling resistance occurs between a rolling object and a surface. For practical purposes, we can stick to wheels as our round objects, since that's how all transportation on land works. For example, trains have solid metal wheels rolling on rails, and they too have rolling resistance slowing the train down.
If we look at the simplest version of rolling resistance, there are only two important quantities for the rolling resistance formula:
RR = μ × N
- μ (Crr) — the coefficient of rolling resistance; and
- N — the normal force, which is the vertical load the surface supports.
In reality, the situation is much more complex, since determining the value of μ is very tricky. In general, μ depends on the surfaces touching (wheel and tarmac/rail/ground), but in many cases it may even depend on speed, pressure, temperature, lubrication, and many other factors.
So, in answering the question "What is rolling resistance caused by?", the simplest answer is the friction between the wheels and the surface. The longer, more precise answer is that rolling resistance is caused by anything in the wheel or the surface that takes energy away from the forward movement of the vehicle. That's exactly why we created this calculator — so you don't have to do all that research yourself.
How to calculate rolling resistance using the rolling resistance calculator?
The calculator works in both the US customary and metric systems. Just follow these steps:
- Choose your unit system (metric: kg, km/h, km — or imperial: lb, mph, mi).
- Enter the mass (weight) of your vehicle or object. On a flat road the normal force equals the weight; on a slope the calculator uses N = m·g·cos(θ).
- Pick the surface / tire type to set the rolling resistance coefficient (Crr), or enter your own custom Crr.
- Optionally set the road grade, your speed, and the distance travelled.
- Read the rolling resistance force, the power needed to overcome it, and the energy and fuel lost over the distance.
The normal force is computed as N = m × g × cos(arctan(grade / 100)), where g = 9.80665 m/s², and then the rolling resistance force is simply RR = Crr × N.
Rolling resistance and drag: how to reduce fuel consumption?
At low speeds, rolling resistance is the dominant force slowing your car down. As speed rises, aerodynamic drag (which grows with the square of speed) takes over. To reduce fuel consumption you can attack both: keep your tires correctly inflated and choose low rolling resistance tires to cut Crr, and reduce your frontal area and drag for high-speed driving.
This calculator estimates how much fuel is burned just to overcome rolling resistance over a given distance, using the engine efficiency you specify and the energy content of gasoline (≈ 34.2 MJ per litre). It then converts that into a cost in the currency of your choice — US dollars, Russian rubles, euros, pounds, yuan, yen, rupees, or Brazilian reais.
Car and bicycle rolling resistance
Typical rolling resistance coefficients (Crr):
- Car tires on asphalt: 0.013
- Low rolling resistance car tires: 0.009
- Truck tires: 0.006
- Bicycle racing tires: 0.004
- Mountain bike tires: 0.012
- Train (steel wheel on steel rail): 0.001
- Car tire on sand: 0.30
This is why trains are so efficient at moving heavy loads — steel-on-steel gives an extremely low Crr — and why a racing bicycle rolls so much further than a mountain bike on the same road.
Summary: what you should have learned
Rolling resistance is a friction force that opposes motion, equal to the rolling resistance coefficient times the normal force. It does not depend on tire size, but it does depend on weight, surface, and tire construction. Lowering Crr — by choosing better tires or a smoother surface — directly reduces the force, the power, and the fuel needed to keep moving.
FAQs
Does rolling resistance depend on speed?
In the simplest model, the rolling resistance force does not depend on speed — it stays constant. However, the power required to overcome it grows linearly with speed, because power = force × velocity. In reality, Crr can rise slightly at very high speeds.
Do bigger tires have more rolling resistance?
Not necessarily. Rolling resistance force depends on weight and the coefficient Crr, not on tire size. A wider tire can actually have a lower Crr at the same pressure because it deforms less.
Are low rolling resistance tires worth it?
For most everyday drivers the fuel savings are modest, but over many years and high mileage they can add up. Use this calculator to estimate the fuel and money saved by lowering your Crr from, say, 0.013 to 0.009.
Why does this calculator ask for engine efficiency?
To turn the mechanical energy lost to rolling resistance into a real fuel figure, we divide by the engine efficiency (typically ~25% for a gasoline car). A more efficient engine wastes less fuel to deliver the same wheel energy.