Angular Momentum Calculator
Enter a mass, a tangential speed, and a radius to get the angular momentum of a point mass moving in a circle, in kg·m²/s.
One number, three inputs
Enter the mass, the tangential speed, and the radius and the calculator returns the angular momentum (m·v·r) about the axis in kg·m²/s.
Use SI units
Mass in kilograms, speed in metres per second, and radius in metres give the angular momentum in kg·m²/s — divide km/h by 3.6 to get m/s first.
What is angular momentum?
The momentum of rotation
This angular momentum calculator finds how much rotational motion a moving object carries about an axis. Angular momentum is the rotational counterpart of linear momentum: where linear momentum tracks straight-line motion, angular momentum tracks motion around a point. For a point mass travelling in a circle it depends on three things — how heavy the object is, how fast it moves along its path, and how far that path sits from the axis. Multiply those together and you get the angular momentum in kilogram-square-metres per second, the quantity that stays conserved when no external torque acts.
Enter a mass in kilograms, a tangential speed in metres per second, and a radius in metres to get the angular momentum in kg·m²/s instantly.
The angular momentum of a point mass moving in a circle is the mass multiplied by the tangential speed multiplied by the radius.
L = m × v × rTake a 2 kg ball whirling on a 0.5 m string at a tangential speed of 3 m/s. Multiply the mass by the speed (2 × 3 = 6), then by the radius (6 × 0.5 = 3), and the angular momentum is 3 kg·m²/s. Each factor enters in the first power, so doubling the mass, the speed, or the radius simply doubles the result — the radius acts as the lever arm that converts the linear momentum (m·v) into angular momentum about the axis.
The formula is exact for a point mass, but a couple of points are worth keeping in mind.
Point-mass form and consistent units
This calculator uses the point-mass form, L = m·v·r — valid for a small object on a circular path. For an extended body that spins about its own axis, angular momentum is L = Iω, where I is the moment of inertia and ω the angular speed, which this tool does not compute. Keep your units consistent — kilograms, metres per second, and metres — or the result will be wrong: convert km/h to m/s by dividing by 3.6 before you enter the speed.