About This Tool
The Circle Calculator computes area, circumference, diameter and arc length from any single measurement — radius, diameter or circumference.
Frequently Asked Questions
What is the formula for circle area?
Area = π × r², where r is the radius.
How is circumference calculated?
Circumference = 2 × π × r, or equivalently π × diameter.
Can I enter the circumference to find the radius?
Yes, enter any one of the three values and all others are calculated automatically.