Newton's second law
Force equals mass times acceleration: F = m × a. Choose which quantity to find and enter the other two in any common units — newtons, kilonewtons, kilogram-force or pound-force; kilograms, grams or pounds; m/s², ft/s² or g.
The result also shows the force in N, kgf and lbf, and the acceleration as a multiple of Earth's gravity.
How to calculate force
- 1
Choose what to solve for
Force, mass or acceleration.
- 2
Enter the other two
With their units.
- 3
Read the result
In the unit you choose.
Key features
Solve any variable
F, m or a.
Many units
N, kN, kgf, lbf, dyn and more.
g-force
Acceleration relative to gravity.
Instant
Updates as you type.
Common uses
- Physics homework: F = ma problems.
- Engineering: Loads and forces.
- Everyday curiosity: Your weight in newtons.
Tips and good to know
- Weight is the force of gravity: W = m × 9.80665 m/s².
- 1 kgf is the weight of 1 kg on Earth — about 9.81 N.
Frequently asked questions
What is the formula for force?
F = m × a. A 70 kg mass accelerating at 9.81 m/s² experiences about 686 N.
What is a newton?
The force that accelerates 1 kg at 1 m/s².
How do I convert kgf to newtons?
Multiply by 9.80665.