Force Calculator (F = ma)
By Santaji GadepatilinUpdated October 27, 2026
m/s²
calculated
Type in any field to change it. Press × on a value to calculate that field instead.
Force (N) vs Acceleration — other inputs held at your current values.
How to use this calculator
Enter any two of mass, acceleration and force. The third is calculated, in newtons, kN, kgf or lbf.
The formula
F = m × a
Worked example
A 1,200 kg car accelerating at 3 m/s² needs a net force of 1,200 × 3 = 3,600 N (3.6 kN, about 809 lbf).
Net force
F is the net force — the total after friction, drag and other forces are taken into account. A car’s engine must provide more than 3,600 N to overcome rolling resistance and air drag as well.
Units of force
| Unit | In newtons |
|---|---|
| 1 kN | 1,000 N |
| 1 kgf | 9.81 N |
| 1 lbf | 4.448 N |
| 1 dyne | 0.00001 N |
Frequently asked questions
What is Newton's second law?
The net force on an object equals its mass times its acceleration — F = ma.
What is a newton?
The force needed to accelerate 1 kg at 1 m/s². It is roughly the weight of a small apple.
Is force the same as weight?
Weight is a specific force — the pull of gravity, m × g. Use the weight calculator for that.