Calculate the area of a circle easily using radius or diameter with accurate results for math, engineering, and daily use.

The area of a circle calculator will compute the surface of a circle using a radius or a diameter.

Aug 1, 2025 · Use this circle calculator to find the area, circumference, radius or diameter of a circle. Given any one variable A, C, r or d of a circle you can calculate the other three unknowns.

Find circle area using radius, diameter, or circumference. Instant calculations with detailed working and visual results.

The calculator automatically converts between radius and diameter, providing you with complete circle information including area, circumference, and both radius and diameter values.

Calculate the area of a circle given the radius, diameter, or circumference. Plus learn the formulas and steps to find a circle's area.

Calculate the area of a circle given its radius, diameter, or circumference. Perfect for geometry students, engineers, and designers working with circular shapes.

This calculator will calculate the area of a circle given its diameter, using the famous formula area = pi times (d/2) squared. It supports different units such as meters, feet, and inches. Just type …

The diameter is the length across the circle through its center - essentially double the radius. To find the area using the diameter (d), we modify our formula to A = π (d/2)².

Free online circle area calculator. Calculate the area of a circle using radius, diameter, or circumference with step-by-step solutions and visualizations.