Area for common 2D shapes — square, rectangle, triangle, circle, trapezoid or parallelogram.
This calculator uses the base-and-height method (Area = ½ × base × height), which needs the perpendicular height to the base — not all three side lengths like a full triangle solver. It's the fastest way to get area when you already know a base and its height.
Circumference is just the name for a circle's perimeter — the distance around its curved boundary, computed as 2πr. The calculator labels it correctly for the shape you've selected rather than reusing the straight-edge term "Perimeter".
A trapezoid has two parallel sides of different lengths. Base a and Base b are those two parallel sides, and the area formula ½(a+b)h averages them before multiplying by the height between them.