How to Use the Trapezoid Area Calculator
A trapezoid is a quadrilateral with one pair of parallel sides — the top and bottom. Its area equals the average of those two parallel sides multiplied by the height: area = (top + bottom) × height ÷ 2. Its perimeter is simply all four sides added together: top, bottom, left side, and right side. Enter all five values — top, bottom, height, left side, and right side — to see both the area and perimeter at once.
For example, a trapezoid with a top of 4cm, bottom of 8cm, and height of 5cm has an area of (4+8)×5÷2 = 30cm². Adding a left side of 4.3cm and a right side of 5.1cm gives a perimeter of 4+8+4.3+5.1 = 21.4cm. Notice the area calculation never needs the two slanted sides, but getting an accurate perimeter requires knowing all four side lengths.
Trapezoid shapes appear often in roof structures, road cross-sections, and bridge designs. Every input must be greater than 0 — a zero, negative, or empty value triggers a clear error message instead of a wrong result. Whether you're learning quadrilateral area formulas in school or estimating materials for a trapezoid-shaped project, this calculator handles both values at once.
Frequently Asked Questions
Area = (top + bottom) × height ÷ 2 — the average of the two parallel sides times the height.
Add all four sides together: the top, bottom, left side, and right side.
This calculator requires the height directly. Deriving height from side lengths alone needs a separate trigonometric calculation.