Weight Formula
The weight formula W = mg calculates the gravitational force on an object.
Learn how weight differs from mass with clear examples.
The Formula
W = mg
Weight is the force of gravity acting on an object. It equals mass multiplied by the gravitational acceleration.
Variables
| Symbol | Meaning |
|---|---|
| W | Weight (measured in newtons, N) |
| m | Mass of the object (measured in kilograms, kg) |
| g | Acceleration due to gravity (9.81 m/s² on Earth) |
Example 1
What is the weight of a 75 kg person on Earth?
Identify the values: m = 75 kg, g = 9.81 m/s²
Apply the formula: W = mg = 75 × 9.81
W = 735.75 N
Example 2
A crate weighs 196.2 N on Earth. What is its mass?
Rearrange the formula: m = W / g
Substitute: m = 196.2 / 9.81
m = 20 kg
When to Use It
Use the weight formula when you need to convert between mass and gravitational force.
- Calculating how much force gravity exerts on an object
- Converting mass (kg) to weight (N)
- Comparing weight on different planets (change g accordingly)
- Engineering and construction load calculations