⭕Circle Calculator

Calculate circumference, area, diameter, and radius of a circle.

Sector angle (°) — optional

About Circle Calculator

Calculate any property of a circle — radius, diameter, circumference, and area — given any one known value. Enter the radius, diameter, circumference, or area and instantly compute all other properties using π. Also calculates sector area and arc length for a given central angle.

How to Use Circle Calculator

1
Enter one known value
Type any one measurement — radius, diameter, circumference, or area.
2
View all properties
All other circle properties are calculated and displayed instantly.
3
Calculate sector values
Optionally enter a central angle to compute arc length and sector area.

Common Use Cases

Calculating circumference for fencing or trim around circular areas
Finding circle area for flooring and material estimates
Solving circle geometry problems in maths courses
Calculating wheel, gear, or pipe circumferences in engineering

Frequently Asked Questions

Which circle properties can I calculate?

Radius, diameter, circumference (perimeter), area, sector area, and arc length. Enter any single known value and all others are calculated automatically.

Can I calculate the arc length for a given angle?

Yes — enter the central angle in degrees or radians along with the radius to calculate the arc length and sector area.