Area Calculator

This tool computes both the area and perimeter (or circumference) of five geometric shapes: rectangle, circle, triangle, trapezoid, and ellipse. Each shape takes the dimensions you enter in the chosen unit and reports area in square units and perimeter in linear units. For the triangle it assumes an isosceles layout when estimating the sides, for the trapezoid it assumes the top and bottom bases are parallel and centered, and for the ellipse perimeter it uses Ramanujan's approximation.

1. Pick a Shape from the dropdown (rectangle, circle, triangle, trapezoid, or ellipse). 2. Pick the measurement Unit (mm, cm, m, km, in, ft, yd, or mi). 3. Fill the inputs that appear for the chosen shape - rectangle needs Length and Width, circle needs Radius, triangle needs Base and Height, trapezoid needs Top base, Bottom base and Height, ellipse needs Semi-major and Semi-minor axes. 4. Press Calculate to see the Area (unit squared) and Perimeter (unit). 5. Optionally press Add to summary to stack several shapes and view a combined total area and perimeter, convertible to any summary unit.

Rectangle: area = length * width, perimeter = 2 * (length + width). Circle: area = pi * r^2, circumference = 2 * pi * r. Triangle: area = 0.5 * base * height; perimeter uses the isosceles side = sqrt(height^2 + (base / 2)^2). Trapezoid: area = 0.5 * (topBase + bottomBase) * height; leg = sqrt(height^2 + ((bottomBase - topBase) / 2)^2). Ellipse: area = pi * a * b; perimeter (Ramanujan) = pi * (3 * (a + b) - sqrt((3a + b) * (a + 3b))).