Car Center of Mass Calculator

Use this car center of mass calculator and find the exact position of the center of gravity of your car.

Centre of mass1.08 mmeasured on the same scale as the positions you gave

Reduced mass480 kgalways smaller than either mass — 60% of the lighter one

Total mass2 Mg

Distance from the first mass1.08 m40% of the way to the second

Distance from the second mass1.62 m

Mass split60% / 40%the centre of mass sits closer to the heavier one, in inverse proportion to the distances

Load at the first position11.768 kNtreating the separation as a wheelbase and the centre of mass as the load point

Load at the second position7.8453 kN

Front to rear distribution60% / 40%

Reduced mass if the masses were equal500 kga quarter of the total, which is the maximum a reduced mass can ever reach

Reduced mass with an infinitely heavy partner800 kgit tends to the lighter mass — which is why a planet orbiting a star can be treated as if the star were fixed

The formula

reduced mass = m₁m₂ ÷ (m₁+m₂); centre of mass = Σmx ÷ Σm

Two bodies become one

Reduced mass is the trick that turns a two-body problem into a one-body problem. Two masses orbiting each other behave exactly like a single body of reduced mass m₁m₂/(m₁+m₂) orbiting a fixed point, which is why the same formula appears in orbital mechanics, collision physics and molecular vibration.

It is always smaller than either mass, and it has two useful limits. When the masses are equal it is a quarter of the total, which is the largest it can ever be. When one mass hugely exceeds the other it tends to the lighter mass alone — which is the justification for treating the Sun as stationary while a planet orbits it.

Centre of mass is the weighted average of position, and it sits closer to the heavier body in inverse proportion to the distances. In vehicle terms that is weight distribution: the axle nearer the centre of mass carries more load, and the split between them is what the figures above compute.