Area & Perimeter Calculator
Compute the area and perimeter (or circumference) of common 2D shapes — square, rectangle, parallelogram, trapezoid, circle, ellipse, and regular polygon — from their dimensions, with the formulas shown. Pick a shape, enter its dimensions, and the area and perimeter are calculated live. The companion to the 3D Volume & Surface Area calculator. Everything runs locally in your browser.
All formulas use standard plane geometry. The trapezoid perimeter assumes an isosceles trapezoid (equal-length non-parallel sides); the ellipse perimeter uses Ramanujan's approximation, which is exact to within a tiny fraction of a percent. A regular polygon needs at least 3 sides. Results are in square units (area) and linear units (perimeter) of whatever you entered. Everything runs locally — nothing leaves your browser.