TheCalculatory
Science & Engineering · Physics Formula verified

Force Calculator

Pick which quantity to solve for, enter the other two, and see the result instantly — with the formula and a step-by-step proof underneath.

Solve for
kg
0kg500kg1000kg
m/s²
050 m/s²100 m/s²
On-screen number pad
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Force
98.07 N
m = 10kg, a = 9.81m/s²
Weight-equivalent
10.00 kg

Step-by-step proofCheck by hand

How force, mass and acceleration relate

Newton's second law says force equals mass times acceleration — F = ma. Rearranging that one equation gives the other two: mass equals force divided by acceleration, and acceleration equals force divided by mass. A weight-equivalent — the mass that force would weigh under standard Earth gravity — is shown alongside every result as a more intuitive secondary figure.

The formulas

F = ma  ·  m = F ÷ a  ·  a = F ÷ m  ·  weight = F ÷ g

Worked example

A 10 kg mass accelerating at 9.80665 m/s² (standard gravity): force = 10 × 9.80665 = 98.07 N — which weighs the same as its own 10.00 kg mass, as expected at standard gravity.

Frequently asked questions

What is Newton's second law?
Newton's second law states that the net force acting on an object equals its mass times its acceleration: F = ma. It's one of the three laws of motion published by Isaac Newton in 1687, and it's the foundation of classical mechanics.
What units does this calculator use?
Kilograms (kg) for mass, meters per second squared (m/s²) for acceleration, and newtons (N) for force — the standard SI units, where one newton is the force needed to accelerate a one-kilogram mass at one meter per second squared.
What is the weight-equivalent figure?
It's the mass that would weigh the computed force under standard Earth gravity (9.80665 m/s²) — a more intuitive way to picture a force, since most people have a better feel for kilograms than for newtons. It's shown alongside every result regardless of which quantity you solved for.
Sources and method
  • Newton's second law of motion (F = ma) — standard published physics.
Last reviewed: 20 Sep 2026 Sources last verified: 20 Sep 2026 Results use the assumptions explained on this page. Report an error How we check calculations

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