Rolling resistance power calculator
A 1,500 kg car with a rolling coefficient of 0.015 needs about 6 kW of continuous power at 100 km/h just to overcome its tyres' rolling resistance. Get the force in newtons and the power in watts for any mass, Crr and speed. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Mass
- 1,500
- Rolling coefficient
- 0.015
- Speed
- 100
- Mass unit
- kg
- Mass kg
- 1,500
- Speed unit
- kmh
- Speed m s
- 27.7777777778
Every tyre that carries a vehicle deforms slightly under load, and that continuous deformation dissipates energy as heat. The force that models this loss is rolling resistance, and the continuous power needed to overcome it at constant speed is simply that force times road speed. Fleet planners, bicycle coaches, EV range estimators, and vehicle dynamics students all need the same deterministic numbers: newtons of rolling resistance force and watts of rolling resistance power from vehicle mass, a dimensionless rolling coefficient Crr, and speed. This rolling resistance power calculator applies the level-ground model F_rr equals Crr times mass times standard gravity, then multiplies by speed in metres per second, with optional unit conversion for kilograms or pounds and for kilometres per hour, miles per hour, or metres per second.
What rolling resistance force and power mean on level ground
Rolling resistance is the force opposing motion that arises mainly from hysteresis losses inside the tyre carcass and tread as the contact patch repeatedly flattens and recovers. On flat, dry pavement at constant speed, textbooks and vehicle energy models write that force as F_rr equals Crr times the normal load. For a vehicle on level ground the normal load is the weight, mass times standard gravity g equals nine point eight zero six six five metres per second squared, so F_rr equals Crr times m times g.
The dimensionless coefficient Crr depends on tyre construction, inflation, temperature, road texture, and to a lesser extent speed; typical car values sit roughly between zero point zero one and zero point zero two, low-resistance touring bicycle tyres may be near zero point zero zero four to zero point zero zero eight, and soft off-road tyres can be higher.
Continuous mechanical power to overcome that force at speed v is P equals F_rr times v, or equivalently Crr times m times g times v when mass is in kilograms and speed is in metres per second, giving force in newtons and power in watts. This calculator implements exactly that level-ground tire model. It does not add aerodynamic drag, which grows with speed squared and often dominates highway energy use; it does not include grade force m g sin theta; and it does not fold in drivetrain efficiency.
Those terms belong in a full road-load stack. Use rolling resistance power as the tire-loss building block: compare Crr scenarios, size a small electric motor for a low-speed cart, estimate how much continuous power a heavy truck spends just crushing its tyres at cruise, or teach the difference between force (newtons) and power (watts) with a transparent formula students can recompute by hand.
Who uses rolling resistance power figures
Logistics and fleet planning can estimate continuous power (and therefore energy over time) spent on rolling losses when comparing inflation policies or low-rolling-resistance tyre SKUs without standing up a full multi-body vehicle model. Engineering education and motorsport media can embed the calculator next to explainers of road load without reinventing unit conversion edge cases for zero speed or non-finite mass. Failed validation does not consume balance.
Keep requests small, pin the rounded force and power values in tests, and you get reproducible rolling resistance force and power for comparison tables, LMS modules, and edge workers without hosting custom tire-loss math infrastructure of your own.
What you can do with it
EV and e-bike energy budgets
Estimate continuous tire-loss watts at cruise speed so range models can subtract rolling resistance energy from battery capacity alongside aero and accessory loads.
Tyre and inflation comparisons
Compare force and power for two Crr values at the same mass and speed when evaluating low-rolling-resistance tyres or cold-weather under-inflation scenarios.
Teaching road-load components
Show students how F_rr = Crr·m·g and P = F·v separate tire losses from drag and grade with a deterministic oracle for homework and LMS checks.
FAQ
How is rolling resistance power calculated?
P = F_rr · v after converting speed to metres per second.
Does this include aerodynamic drag or hills?
No. It models level-ground tire rolling resistance only. Add aero (½ρCdAv²) and grade (mg sin θ) in your own stack if you need total road-load power.
What rolling coefficient should I use?
Typical car tyres sit roughly between 0.01 and 0.02, low-resistance touring bicycle tyres near 0.004 to 0.008, and soft off-road tyres higher. The exact value depends on tyre construction, inflation, temperature and road texture.
What is the difference between rolling resistance force and power?
The force, in newtons, is the drag the tyres put on the vehicle: Crr times mass times gravity. The power, in watts, is that force multiplied by speed, so the same force costs more power the faster you go.
Can I enter the weight in pounds or the speed in mph?
Yes. Mass can be in kilograms or pounds, converted with the exact factor of 0.45359237 kg per pound, and speed can be in km/h, mph or metres per second. Force always comes out in newtons and power in watts.
Related tools
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/travel/rolling-resistance-power \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"mass":1500,"rolling_coefficient":0.015,"speed":100}'const res = await fetch("https://api.kit.forhosting.com/travel/rolling-resistance-power", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"mass": 1500,
"rolling_coefficient": 0.015,
"speed": 100
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/travel/rolling-resistance-power",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"mass": 1500,
"rolling_coefficient": 0.015,
"speed": 100
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/travel/rolling-resistance-power", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"mass":1500,"rolling_coefficient":0.015,"speed":100}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"mass":1500,"rolling_coefficient":0.015,"speed":100}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/travel/rolling-resistance-power", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"mass": 1500,
"rolling_coefficient": 0.015,
"speed": 100
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "travel.rolling_resistance_power",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |
Technical notes
Invalid values fail with a clear invalid_input error instead of inventing force or power.
Input contract, units, response shape, and errors
Example: one thousand five hundred kilograms, Crr of zero point zero one five, and one hundred kilometres per hour yields a few hundred newtons of rolling resistance force and several kilowatts of continuous rolling power—numbers you can cross-check as Crr times fifteen hundred times nine point eight zero six six five times one hundred over three point six. POST a JSON body with three required finite numbers: mass (aliases weight, vehicle_mass, vehicle_weight, m), the vehicle mass used for the normal load; rolling_coefficient (aliases crr, Crr, rolling_c, mu_rr, coefficient), the dimensionless Crr between zero and one inclusive; and speed (aliases velocity, v, vehicle_speed), a strictly positive road speed. Optional mass_unit defaults to kg; set lb to enter pounds, which convert with the exact international factor one pound equals zero point four five three five nine two three seven kilograms. Optional speed_unit defaults to kmh; accept mph or m_s for miles per hour or metres per second. Missing fields, empty strings, NaN, Infinity, zero or negative mass or speed, negative Crr, and Crr greater than one all fail with invalid_input messages that name the problem; those validation failures are not billed. On success the body echoes mass, mass_unit, mass_kg after conversion, rolling_coefficient, speed, speed_unit, speed_m_s after conversion, g_m_s2, normal_force_n, force_n, power_w, power_kw, power_hp (mechanical horsepower), the formula strings for force and power, method rolling_resistance_level_ground, and a short notes string reminding callers that aero, grade, and drivetrain are excluded. Pair the result with your own aero or grade model when you need total road-load power; this endpoint implements only the rolling term.
Technical questions
How is rolling resistance force calculated?
On level ground F_rr = Crr · m · g with standard gravity g = 9.80665 m/s². Send positive mass and a non-negative Crr; the API returns force_n in newtons plus the normal load used.
What units can I use for mass and speed?
Mass defaults to kg (or set mass_unit to lb). Speed defaults to kmh; set speed_unit to mph or m_s for miles per hour or metres per second.
What does the rolling resistance power calculator cost?
The browser tool is free. API requests use prepaid KIT balance at $0.002 per successful call; invalid input is not billed.