Solve force, mass or acceleration. This free force calculator uses Newton’s second law F = m × a, with a gravity preset for weight, and shows force in newtons, pounds-force and kilograms-force.
Solve for
newtons
kg
m/s²
Enter the two known values and the calculator finds the third using Newton’s second law, F = m × a. Force is in newtons (N), mass in kilograms, acceleration in m/s².
Force
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Enter two values
Force (N)
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Force (lbf)
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Force (kgf)
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As weight of
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Newton’s second law: F = m × a. One newton accelerates 1 kg at 1 m/s². Weight is force from gravity: W = m × g, with g ≈ 9.81 m/s² on Earth.
Use this free force calculator to find force, mass or acceleration using Newton’s second law, F = m × a. Enter any two values and it solves for the third.
What this force calculator does
A force calculator applies Newton’s second law: force equals mass times acceleration. Give it any two of force, mass and acceleration and it returns the third, plus the force in pounds-force and kilograms-force.
The formula
F = m × a
m = F ÷ a a = F ÷ m
Weight: W = m × g (g ≈ 9.81 m/s²)
A 10 kg mass accelerating at 9.8 m/s² needs about 98 N — roughly the weight of a 10 kg object on Earth.
Units of force
Unit
Equals
1 newton (N)
1 kg·m/s²
1 pound-force (lbf)
4.448 N
1 kilogram-force (kgf)
9.807 N
Force vs weight
Weight is just the force of gravity on a mass: W = m × g. A 70 kg person weighs about 686 N on Earth. Mass stays the same everywhere; weight changes with gravity.
How to use the force calculator
Choose force, mass or acceleration to solve for.
Enter the other two values (use the gravity button for weight).
Read the result, with force in N, lbf and kgf.
Force FAQ
How do I calculate force?
Multiply mass by acceleration: F = m × a. A 10 kg mass at 9.8 m/s² gives about 98 newtons.
How do I find mass or acceleration from force?
Rearrange the formula: mass = force ÷ acceleration, and acceleration = force ÷ mass. The calculator does whichever you select.
What is a newton?
One newton is the force that accelerates a 1 kg mass at 1 m/s². It equals about 0.225 pounds-force.
What's the difference between force and weight?
Weight is the specific force of gravity on a mass, W = m × g. Mass is constant, but weight changes with gravity.
How do I calculate weight from mass?
Multiply mass by gravity (about 9.81 m/s²). Use the gravity button to fill it in — a 70 kg person weighs about 686 N.
Is the force calculator free?
Yes, this force calculator is completely free, needs no sign-up, and gives instant results in your browser.
