Force, Mass and Acceleration Calculator (F = m × a)

Newton's second law

The net force on a body equals its mass multiplied by its acceleration: F = m × a. Force is measured in newtons (N), mass in kilograms (kg) and acceleration in metres per second squared (m/s²). One newton is the force that gives a mass of 1 kilogram an acceleration of 1 m/s².

Rearranged, acceleration is a = F / m and mass is m = F / a. The calculator takes two of the three quantities and solves the third step by step.

What does net force mean?

F in the formula is not a single force but the sum of all forces on the body. If an engine pushes a car with 4000 N while friction and drag pull back with 1000 N, the net force is 3000 N and that is what sets the acceleration.

Example

Accelerating a 1200 kg car at 2.5 m/s² takes a net force of 1200 × 2.5 = 3000 N, which is about 306 kilogram force.

Mass is not weight

Mass is the amount of matter in a body and is the same everywhere. Weight is the force gravity exerts on it: W = m × g. With g about 9.81 m/s² on Earth, a mass of 5 kg weighs 49 N.

Limits

The law holds for bodies of constant mass at everyday speeds. If forces act in different directions, resolve them into components and find the net force first.