The centre of mass decides how a car handles, how much weight shifts under braking and how likely it is to roll over. Race teams measure it with corner scales; you can do the same with a weighbridge and a jack.
How to use the Car Center of Mass Calculator
- Find
- Front axle weight
- Rear axle weight
- Wheelbase L
- Height the rear is raised H
- Wheel radius r
- Front axle weight with rear raised
- Track width T
- Left wheels weight
- Right wheels weight
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
Choose what to find. For the height, weigh the front axle on level ground and again with the rear raised by H (measured at the wheel centres).
Tips
- In equilibrium the forces and the moments both add to zero.
- Pressure is force per area: a smaller area means a higher pressure.
- Check which units your scale or gauge uses before typing.
- Choose the pivot point that eliminates the most unknown forces.
Common mistakes to avoid
- Mixing gauge and absolute pressure.
- Using a diameter instead of a radius when calculating an area.
- Forgetting that mass does not change between planets – weight does.
Inputs explained
| Field | What to enter |
|---|---|
| Find | Choose one: Position between the axles, Height, Lateral position |
| Front axle weight | Units: kg, g, mg, t, lb, oz |
| Rear axle weight | Units: kg, g, mg, t, lb, oz |
| Wheelbase L | Units: m, cm, mm, km, in, ft … |
| Height the rear is raised H | Units: cm, mm, m, in, ft |
| Wheel radius r | Units: cm, mm, m, in, ft |
| Front axle weight with rear raised | Units: kg, g, mg, t, lb, oz |
| Track width T | Units: m, cm, mm, km, in, ft … |
| Left wheels weight | Units: kg, g, mg, t, lb, oz |
| Right wheels weight | Units: kg, g, mg, t, lb, oz |
What each result means
- Distance from the front axle a = [Wheelbase L]×[Rear axle weight]÷([Front axle weight] + [Rear axle weight])
- Distance from the rear axle b = [Wheelbase L] – [Wheelbase L]×[Rear axle weight]÷([Front axle weight] + [Rear axle weight])
- Front weight distribution = [Front axle weight]÷([Front axle weight] + [Rear axle weight])×100
- Height of the centre of mass = [Wheel radius r] + [Wheelbase L]×([Front axle weight with rear raised] – [Front axle weight])÷(([Front axle weight] + [Rear axle weight])×tan(asin([Height the rear is raised H]÷[Wheelbase L])))
- Distance from the left wheels = [Track width T]×[Right wheels weight]÷([Left wheels weight] + [Right wheels weight])
- Left weight distribution = [Left wheels weight]÷([Left wheels weight] + [Right wheels weight])×100
Example values
How the main result changes when Front axle weight changes and everything else stays at the example values above:
| Front axle weight (kg) | Distance from the front axle a (m) |
|---|---|
| 450 | 1.5826 |
| 675 | 1.3236 |
| 900 | 1.1375 |
| 1,125 | 0.9973 |
| 1,350 | 0.8878 |
| 1,800 | 0.728 |
Formula
a = L·W_r / W (from the front axle), b = L − a
h = r + L·(W_f,raised − W_f) / (W·tan θ), θ = arcsin(H/L)
y = T·W_right / W (from the left wheels)
Worked example
Inputs — Find: Position between the axles; Front axle weight: 900 kg; Rear axle weight: 700 kg; Wheelbase L: 2.6 m.
Results — Distance from the front axle a = 1.1375 m; Distance from the rear axle b = 1.4625 m; Front weight distribution = 56.25 %.
Key terms
- Wheelbase
- Distance between front and rear axles.
Frequently asked questions
Why does the centre of mass height matter?
It sets weight transfer in corners and braking, and rollover risk.
How accurate is the raised-axle method?
Very sensitive to small weight changes – raise the car as much as safely possible.
What is a good weight distribution?
Sports cars aim for about 50:50 front to rear.
Do I need to lock the suspension?
Ideally yes, or the suspension movement adds error.