Circle Calculator
Get the area and circumference of a circle from its radius — instantly, in your browser.
Area78.54units²
Circumference31.42units
Diameter10.00units
Area = π·r² and circumference = 2·π·r, where r is the radius. The diameter is twice the radius. With r = 5: area ≈ 78.54, circumference ≈ 31.42.
Questions
How do I find the area of a circle?
Multiply pi (≈3.14159) by the radius squared: Area = π·r². For a radius of 5, that is 3.14159 × 25 ≈ 78.54.