Force calculator: Newton's second law F = ma
Choose the unknown and enter the other two values. Force is shown in newtons, kilonewtons and kilogram-force.
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Processing and privacy: The result is calculated inside your browser and your data is not sent to any server.
How to use it
- Enter what do you want to find?, mass, acceleration and force.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
F = m × a, m = F ÷ a, a = F ÷ m. One newton is 1 kg·m/s², and one kilogram-force is 9.80665 N.
Example
Inputs: What do you want to find? = Force, Mass = 10 kg, Acceleration = 2 m/s², Force = 20 N. Result: Force: 20 N; In kilonewtons: 0.02 kN; In kilogram-force: 2.0394 kgf.
Limits and caveats
- Applies to the net force on the object, not to one force when others such as friction also act.
- Assumes constant mass and speeds far below the speed of light.
Questions about this tool
What is a newton?
The force that gives a 1 kg mass an acceleration of 1 m/s². A small apple weighs about 1 N.
What is the difference between mass and weight?
Mass is the amount of matter in kilograms; weight is the pull of gravity, equal to mass × g in newtons.
Should I enter the total force or one force?
The second law links acceleration to the net force, so subtract opposing forces such as friction first.