Area of Circle Calculator
⚡ Calculate any circle property instantly. Enter radius, diameter, area, OR circumference - get all values with step-by-step solutions.
The Best Circle Calculator Online
Our circle calculator is No signup required of students, engineers, and professionals worldwide. Enter ANY value you know (radius, diameter, area, or circumference) and instantly get ALL circle properties with step-by-step solutions. Perfect for geometry homework, design projects, and quick calculations. No signup, no ads, just instant accurate results.
Area
A = πr²Area equals pi times radius squared
Circumference
C = 2πr = πdDistance around the circle
Diameter
d = 2rDistance across through center
Examples
Circle with radius 5
Circle with diameter 10
Frequently Asked Questions
Is this circle calculator free?
Yes! 100% free with no signup required and no ads.
Why is π used in circle calculations?
π (pi) is the ratio of a circle's circumference to its diameter. It's a mathematical constant that appears in all circle-related formulas.
What's the difference between radius and diameter?
Diameter is the full width of a circle through its center. Radius is half the diameter - the distance from center to edge.