How to calculate the volume of a prism
The volume of a prism is the amount of space inside it. Volume is measured in cubic units, such as , or .
1. Learn the formula
A prism has the same cross-sectional shape all the way along its length.
For example, a triangular prism has a triangle at each end, while a rectangular prism has a rectangle at each end.
2. Example: a triangular prism
A triangular prism with a triangular cross-section and a length of 10 cm.
Suppose the triangle at the end has:
- Base = 6 cm
- Height = 4 cm
- Prism length = 10 cm
Step 1: Calculate the area of the triangular end.
The formula for the area of a triangle is:
Substitute the numbers:
Step 2: Multiply by the length of the prism.
Remember: calculate the area of the end shape first, then multiply it by the prism’s length.
3. Other prism formulas
| Cross-sectional shape | Area of the end | Volume |
|---|---|---|
| Rectangle | ||
| Triangle | ||
| Trapezium |
Here, is the length of the prism.
Exam tip: Always write the final answer in cubic units, such as , because volume measures three-dimensional space.