Force Calculator
Apply Newton’s second law to find force, mass or acceleration.
Please note: Results use idealised models — point masses, no air resistance, ideal gases and uniform materials. Real experiments deviate. Use these for study and estimation, not for engineering sign-off.
What the Force Calculator does
Newton’s second law states that the net force on an object equals its mass times its acceleration. Because the three quantities are locked together, knowing any two gives the third — which is why this one relationship underpins most of mechanics.
Formula
F = m × am = F ÷ aa = F ÷ mWeight W = m × g
Inputs explained
| Input | Unit | Required | Notes |
|---|---|---|---|
| Solve for | one of 3 options | Yes | — |
| Mass | number | In some modes | Shown Solve for is Force (F = ma), or Solve for is Acceleration (a = F/m). |
| Mass unit | one of 6 options | In some modes | Shown Solve for is Force (F = ma), or Solve for is Acceleration (a = F/m). |
| Acceleration | number | In some modes | Shown Solve for is Force (F = ma), or Solve for is Mass (m = F/a). |
| Acceleration unit | one of 4 options | In some modes | Shown Solve for is Force (F = ma), or Solve for is Mass (m = F/a). |
| Force | number | In some modes | Shown Solve for is Mass (m = F/a), or Solve for is Acceleration (a = F/m). |
| Force unit | one of 5 options | In some modes | Shown Solve for is Mass (m = F/a), or Solve for is Acceleration (a = F/m). |
| Gravitational acceleration | m/s² | Optional | Standard gravity on Earth is 9.80665 m/s². The Moon is 1.62, Mars 3.72. Accepts 0 or more. |
How to use it
- Choose Solve for.
- Fill in the remaining inputs the form shows for your choice.
- Optionally add Gravitational acceleration.
- Select Calculate.
Worked example
A 1,200 kg car accelerating at 3.4722 m/s².
- Mass
- 1200 kg
- Acceleration
- 3.4722 m/s²
F = 1200 × 3.4722 = 4,166.6 N. The car’s weight is 1200 × 9.80665 = 11,768 N, so the driving force is about 35% of its weight.
Frequently asked questions
What is a newton?
The force that accelerates 1 kg at 1 m/s². On Earth, holding a small apple takes roughly one newton.
Is weight the same as mass?
No. Mass is how much matter there is, measured in kilograms. Weight is the force gravity applies to that mass, measured in newtons, and it falls to about a sixth on the Moon.