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Formula Reference
Perimeter of a Trapezoid
The perimeter of a trapezoid calculator finds any of these five values: Perimeter, Base 1, Base 2, Side 1 or Side 2. The bases are the two parallel sides, and the sides (also called legs) are the two that join them. Enter four values and the missing one is calculated automatically.
How it works
The perimeter is the total length around the trapezoid, so it is the sum of its four sides:
\[ Perimeter = Base_1 + Base_2 + Side_1 + Side_2 \]
To find a missing side, subtract the other three from the perimeter. For the trapezoid to close, the two sides must be able to join the bases: the difference between the bases has to be greater than the difference between the sides and smaller than their sum.
Example
A trapezoid has bases of 4 and 8 and two sides of 5. The perimeter is 4 + 8 + 5 + 5 = 22. If you know the perimeter is 22, the bases are 4 and 8 and one side is 5, leave the other side empty and the calculator finds 5.
External Resources
- Trapezoid properties, perimeter and area — Math is Fun
- Trapezoid definition and properties — Wikipedia