Force Calculator

Force calculator at a glance#

A force calculator finds force from mass and acceleration using Newton's second law of motion, written F = ma. Force equals mass times acceleration, so a 10 kg object accelerating at 2 m/s² needs a force of 20 N. The same formula rearranges to find mass (m = F/a) or acceleration (a = F/m).

The SI unit of force is the newton (N), defined as kg·m/s², so keep mass in kilograms and acceleration in meters per second squared to get a result in newtons. To find force by hand, multiply the mass by the acceleration. To find a missing value instead, divide: acceleration is force divided by mass, and mass is force divided by acceleration. For example, 500 N on a 25 kg object gives 20 m/s².

Enter any two of force, mass, and acceleration in the calculator above and it returns the third. Net force is the total of all forces acting on the object, so account for friction and other forces when a real result differs from the plain F = ma figure.

How to use the force calculator#

Enter any two of force, mass and acceleration, and the calculator returns the third using Newton's second law, F = ma. Keep mass in kilograms and acceleration in meters per second squared to get force in newtons (N). The same formula rearranges to a = F / m for acceleration and m = F / a for mass.

Example: finding acceleration#

A force of 500 N acts on a 25 kg object. Acceleration is force divided by mass: 500 / 25 = 20 m/s². The object speeds up by 20 meters per second every second the force is applied.

Example: finding mass#

An object accelerates at 2 m/s² under a force of 800 N. Mass is force divided by acceleration: 800 / 2 = 400 kg.

Net force and friction#

F = ma uses the net force, which is the sum of every force on the object. Friction opposes motion and works out to f = mu x N, where mu is the coefficient of friction and N is the normal force. Subtract friction (and any other opposing force) from the applied force before using F = ma, or the predicted acceleration will be too high.

Frequently asked questions#

What is the force formula?#

F = ma, from Newton's second law. Force equals mass times acceleration. A 1500 kg car accelerating at 3 m/s² needs 1500 x 3 = 4500 N.

How do I find acceleration or mass from force?#

Rearrange F = ma. Acceleration is a = F / m, and mass is m = F / a. A 500 N force on 25 kg gives 500 / 25 = 20 m/s².

What is the unit of force?#

The SI unit is the newton (N), defined as kg·m/s². One newton is the force that accelerates a 1 kg mass at 1 m/s².

What is the difference between contact and non-contact force?#

A contact force needs the objects to touch, such as friction or tension. A non-contact force acts across a distance, such as gravity or magnetism.

How does friction affect a force calculation?#

Friction resists motion, so it reduces the net force. It equals f = mu x N. Subtract it from the applied force before applying F = ma to get the real acceleration.