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

See How to Calculate the Area below, but first the calculator: Enter the radius, diameter, circumference or area of a Circle to find the other three.

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.

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 …

Need to know the area of a circle using just its diameter? Use our Diameter to Area Calculator to get fast, accurate results for all your circular measurement needs.

Jul 2, 2025 · This calculator determines the area of a circle using either the radius or the diameter. You may also enter a custom value for π, or use the default value of 3.14159.

Free online circle area calculator to find the area of a circle from radius or diameter. Includes formulas, examples, and comparison tables for different circle sizes.

Square the radius and multiply by π. The most common method for finding area. Square the diameter, multiply by π, then divide by 4. Square the circumference and divide by 4π. The …

Quickly calculate the area of a circle using radius or diameter. This free, easy-to-use circle area calculator works great on mobile and desktop.

Oct 29, 2025 · To find the area of a circle, use the formula A = π • r2, where r is the radius of the circle. If you only know the diameter of the circle, then use the formula A = π • (d/2)2 where d …