A trapezoid’s area equals the average of its parallel sides times its height.
How to use the Trapezoid Area Calculator
- Parallel side a
- Parallel side b
- Height
- Want to work backwards? Type a value into Area and Height is calculated for you.
Results update as you type, and every field accepts the units shown in its menu.
How it works
Add the two parallel sides, halve the sum and multiply by the perpendicular height.
Inputs explained
| Field | What to enter |
|---|---|
| Parallel side a | Units: m, cm, mm, km, in, ft … |
| Parallel side b | Units: m, cm, mm, km, in, ft … |
| Height | Units: m, cm, mm, km, in, ft … |
What each result means
- Area = ([Parallel side a] + [Parallel side b])÷2 × [Height]
- Median (midsegment) = ([Parallel side a] + [Parallel side b])÷2
Example values
How the main result changes when Height changes and everything else stays at the example values above:
| Height (m) | Area (m²) |
|---|---|
| 2 | 13 |
| 3 | 19.5 |
| 4 | 26 |
| 5 | 32.5 |
| 6 | 39 |
| 8 | 52 |
Formula
Area = (a + b) ÷ 2 × hWorked example
Inputs — Parallel side a: 8 m; Parallel side b: 5 m; Height: 4 m.
Results — Area = 26 m²; Median (midsegment) = 6.5 m.
Frequently asked questions
Is a trapezoid the same as a trapezium?
In the U.S. “trapezoid”; in the UK and elsewhere “trapezium”.
Do I need the slanted sides?
Not for area, only for perimeter.
What formula does the Trapezoid Area Calculator use?
Area = (a + b) ÷ 2 × h.
Can I work backwards from the result?
Yes. Type the result you want into Area and the calculator finds the matching height.