Force Calculator (F = ma)
Calculate force, mass, or acceleration using Newton's Second Law: F = m × a. Choose what you want to find, select your units, and get results with multi-unit conversions.
Newton's Laws of Motion
An object remains at rest or in uniform motion unless acted upon by an external net force.
The net force on an object equals its mass multiplied by its acceleration. This is the basis of this calculator.
For every action there is an equal and opposite reaction.
Common Force Examples
| Example | Force (N) |
|---|---|
| Weight of 1 kg (gravity) | 9.81 N |
| Weight of 100 kg person | 981 N |
| Bite force (human) | ~700 N |
| Car engine thrust | ~5,000–15,000 N |
| Jet engine thrust | ~100,000–400,000 N |
| 1 lbf | 4.448 N |
| 1 kgf | 9.807 N |
| 1 dyne | 0.00001 N |
Frequently Asked Questions
The Newton is the SI unit of force. One Newton is the force needed to accelerate a 1 kg mass at 1 m/s². It is named after Sir Isaac Newton. In everyday terms, one Newton is roughly the weight force of a 102 g object under Earth's standard gravity (9.80665 m/s²).
Mass is the amount of matter in an object (measured in kg) and does not change regardless of location. Weight is the gravitational force acting on that mass (measured in Newtons) and depends on gravity. Weight = mass × gravitational acceleration. On the Moon (g ≈ 1.62 m/s²), a 70 kg person weighs only about 113 N instead of 686 N on Earth.
G-force (or gravitational force equivalent) measures acceleration relative to Earth's standard gravity (g = 9.80665 m/s²). 1g = 9.81 m/s². Humans can tolerate about 5g sustained; fighter pilots experience 9g in tight turns; astronaut launch forces are around 3g.
Multiply Newtons by 0.224809 to get lbf. For example, 100 N × 0.224809 = 22.48 lbf. To convert lbf to N, multiply by 4.44822.
Kilogram-force (kgf) is the force exerted by gravity on a 1 kg mass under standard Earth gravity. 1 kgf = 9.80665 N exactly. It is a non-SI unit still commonly used in mechanical engineering and everyday settings.
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