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Moment of a force calculator

GCSEA-level Forces

The moment of a force about a pivot is the force multiplied by its perpendicular distance from the pivot.

M = F d

This free calculator is for GCSE and A-level physics. Choose the quantity you want to find, enter the other values with their units, and it shows the working in the layout used in exams, with the answer to the number of significant figures you choose. The values shown are an example. Change them to your own.

Quantity to find

24.0 N m N m

Working

  1. Write the equation
    M = F d
  2. Substitute the values
    M = 40 × 0.6
  3. Calculate
    M = 24 N m
  4. Give the answer to 3 significant figures
    M = 24.0 N m

Worked example

Find M, the moment. Given: force F = 40.0 N; perpendicular distance from the pivot d = 0.600 m.

  1. Write the equation
    M = F d
  2. Substitute the values
    M = 40 × 0.6
  3. Calculate
    M = 24 N m
  4. Give the answer to 3 significant figures
    M = 24.0 N m

Symbols and units

SymbolQuantitySI unit
MMomentN m
FForceN
dPerpendicular distance from the pivotm

Moment of a force: rearranged

  • To find moment: M = F d
  • To find force: F = M / d
  • To find perpendicular distance from the pivot: d = M / F

Exam tip

For a balanced object, the clockwise moments equal the anticlockwise moments. Use the perpendicular distance.

Common questions

What is the formula for moment of a force?

The equation is M = F d, where M is the moment (N m); F is the force (N); d is the perpendicular distance from the pivot (m).

What units should I use for moment of a force?

In SI units: moment in N m, force in N, perpendicular distance from the pivot in m. The calculator also accepts common alternatives such as kilometres, grams or minutes, and converts them for you.

How do I rearrange M = F d?

Rearranging gives these forms: to find moment: M = F d. to find force: F = M / d. to find perpendicular distance from the pivot: d = M / F.

Practise moment of a force questions

Press the button for a question with random numbers. Work it out on paper first, then type your answer.

Related

Read the full explanation on the Moment of a force formula page. More forces equations: Newton’s second law, Weight, Hooke’s law, Pressure, Pressure in a liquid, Density, Horizontal component of a force, Vertical component of a force. See the full list on the physics equation calculator page.