Force Calculator

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Newton’s second law says net force equals mass times acceleration: F = ma. Pushing a 10 kg box so it speeds up at 3 m/s² takes F = 10 × 3 = 30 N. Weight is the same law with a = g: a 70 kg person weighs 686.5 N on Earth.

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Acceleration a (m/s²)

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Net force

\(\displaystyle F = 30\ \text{N}\)

Newton’s second law: force = mass × acceleration (1 N = 1 kg·m/s²).

Newtons	30 N
Kilonewtons	0.03 kN
Pound-force	6.74427 lbf

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\(F = ma = 10\ \text{kg} \times 3\ \text{m/s}^{2} = 30\ \text{N}\)

How to use the force calculator

Choose what to find: force, mass, acceleration or weight.
Enter the other two quantities and their units.
Press Calculate to see the answer in several units with the working.

Newton’s second law

\(F = ma\), so \(m = \frac{F}{a}\) and \(a = \frac{F}{m}\). One newton is the force that gives 1 kg an acceleration of 1 m/s²: \(1\ \text{N} = 1\ \text{kg}\cdot\text{m/s}^{2}\). F is the net (total) force; balanced forces give zero acceleration.

Mass vs weight

Mass (kg) is the amount of matter and stays the same everywhere. Weight (N) is the force of gravity on that mass, \(W = mg\). A 70 kg astronaut weighs about 686 N on Earth, 113 N on the Moon and 260 N on Mars.

Units

Unit	In newtons
1 kN	1,000 N
1 lbf (pound-force)	4.448 N
1 kgf (kilogram-force)	9.807 N

Force and Newton’s second law quiz: 10 questions

Test yourself with 10 multiple-choice questions. Choose an answer and press Submit to see if you are right and why. Your score appears at the end.

Frequently asked questions

What is the formula for force?

F = ma: net force equals mass times acceleration.

What is the difference between mass and weight?

Mass measures matter in kilograms and is the same everywhere; weight is the gravitational force W = mg in newtons and depends on where you are.

How do I calculate weight?

Multiply the mass in kilograms by the gravitational acceleration: 9.80665 m/s² on Earth.

What is a newton?

The SI unit of force: the force that accelerates 1 kg at 1 m/s².

Does F = ma use the total force?

Yes. Use the net force, the vector sum of all forces acting on the object.

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Effortless Math Team

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