Newton's second law tool

Force Calculator

Solve force, mass, or acceleration from two known values using F = m × a.

Enter two known values

Solve a force problem

Free tool
N

This is the value being calculated.

kg

Amount of matter in the object.

m/s²

Change in velocity per unit time.

Use kilograms for mass, meters per second squared for acceleration, and newtons for force.

Try an example:

Your force result will appear here

Choose the missing variable and enter the other two known values.

Newton's second law

What is force?

Force is a push or pull that can change an object's motion. The net force on an object equals its mass multiplied by its acceleration.

Formula

Force formula

ForceF = m × a

  • F is net force in newtons.
  • m is mass in kilograms.
  • a is acceleration in meters per second squared.

Worked example

A 10 kg object accelerates at 3 m/s²

  1. Write the formula: F = m × a.
  2. Substitute the values: F = 10 × 3.
  3. Calculate the force: F = 30 N.

Rearranged equations

Solve for mass or acceleration

Mass

m = F ÷ a

Divide force by non-zero acceleration.

Acceleration

a = F ÷ m

Divide force by a positive mass.

Net force

Use the combined force on the object

Newton's second law uses net force, which is the vector sum of all forces. Forces acting in opposite directions should use opposite signs before they are combined.

Direction

Interpret positive and negative values

A positive or negative force indicates direction relative to the chosen axis. Because mass is positive, force and acceleration point in the same direction.

Units

Standard SI units

One newton equals one kilogram meter per second squared. Convert grams to kilograms and other acceleration units to meters per second squared before using the calculator.

One newton1 N = 1 kg·m/s²

Assumptions

What the calculation represents

  • Force should represent the net force.
  • Mass must be greater than zero.
  • Direction signs must be used consistently.
  • The calculation uses SI units without automatic conversion.

Related tools

Use the Acceleration Calculator to calculate acceleration from initial velocity, final velocity, and time.

Use the Rate of Change Calculator for general change-over-interval calculations, and review the Tables and Graphs Guide when presenting force and acceleration data.

Related calculators

Questions and answers

Force calculator FAQ

What formula does the force calculator use?

It uses Newton's second law: force equals mass multiplied by acceleration, F = m × a.

What is one newton?

One newton is the force needed to accelerate one kilogram of mass by one meter per second squared.

Can force and acceleration be negative?

Yes. A negative sign indicates direction relative to the chosen positive axis.

What units should I use?

Use kilograms for mass, meters per second squared for acceleration, and newtons for force.

Accuracy and transparency

Created and maintained by our editorial team

This physics calculator is maintained by the Science Lab Tools Editorial Team. Its calculation logic is tested with representative inputs, while the supporting guidance is checked for formula clarity, units, assumptions, and common mistakes.

Learn more about our formula-review and correction process, or read about Science Lab Tools.

  • Calculation logic tested
  • Variables and units explained
  • Assumptions stated clearly
  • Corrections handled transparently