What is the Trapezoid Area Calculator?
A trapezoid has one pair of parallel sides. Its area is the average of those two sides multiplied by the height between them.
How to use the Trapezoid Area tool
- Enter Parallel side a, Parallel side b and Height.
- The result updates instantly as you type, or press Calculate.
- Use Try an example to see how it works, and Reset to start again.
Formula
Area = (a + b) ÷ 2 × h.
Worked example
With sides 8 and 12 and a height of 5: (8 + 12) ÷ 2 × 5 = 50.
Frequently asked questions
What is the area formula for a trapezoid?
Area = (a + b) ÷ 2 × h, where a and b are the parallel sides and h is the height.
Is the height the slanted side?
No. It is the perpendicular distance between the parallel sides.
Trapezoid area examples
Area = (base 1 + base 2) ÷ 2 × height.
| Base 1 | Base 2 | Height | Area |
|---|---|---|---|
| 3 | 5 | 2 | 8 |
| 4 | 6 | 3 | 15 |
| 5 | 7 | 4 | 24 |
| 6 | 10 | 5 | 40 |
| 8 | 12 | 6 | 60 |
| 10 | 14 | 8 | 96 |
| 10 | 20 | 10 | 150 |
| 12 | 18 | 9 | 135 |
| 15 | 25 | 12 | 240 |
| 20 | 30 | 15 | 375 |
FAQ
What is the trapezoid area formula? A = ½ (a + b) × h, where a and b are the parallel sides and h is the perpendicular height.
Do I use the slanted side? No. Use the perpendicular height between the parallel sides.
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Checked by Calcovate · Formula tested against worked examples · Updated 7 Nov 2026 · How we check our calculators.