What This Calculator Does

The Trapezoid Area Calculator takes two parallel bases and the perpendicular height. It gives the area in the square of your chosen length unit, plus square metres and square feet. A labelled schematic identifies a, b and h; the drawing does not scale to the entered measurements.

When to Use It

Use it for a geometry problem or a flat region measured as a trapezoid. For triangles use the triangle calculator; for combined regions use square footage. A slanted side alone is not enough to determine height.

Inputs Explained

Both bases and height must be positive. Choose metres, centimetres, millimetres, feet or inches. Changing the unit converts valid dimensions to preserve their physical size. Enter plain decimals or scientific notation, without units, expressions or thousands separators.

Confirm that the two entered bases are parallel, then measure height perpendicular to them. Leaning the trapezoid left or right does not change its area when bases and height stay the same. If a diagram labels only a slanted side, determine perpendicular height separately before using this tool.

For example, 80 cm, 120 cm and 50 cm produce 5000 cm², or 0.5 m². This equals the result from 0.8 m, 1.2 m and 0.5 m. Entering centimetre values while metres are selected would multiply the area by ten thousand.

How the Calculation Works

$$A=\frac{a+b}{2}h$$