Find the area of a circle from radius, diameter or circumference. Uses A = pi r^2, reverses missing dimensions and converts area units.
Use this area of a circle calculator to find circle area from radius, diameter, or circumference. It also works in reverse, so you can start from a known area and solve the missing circle dimension.
The main formulas are A = pi r^2, A = pi d^2 / 4, and A = C^2 / (4pi). That makes the calculator useful for geometry, flooring, round tables, circular plots, pipe cross-sections, and any problem where a round area must be measured or compared.
