Circle & Sector Workspace
Enter radius and angle once to calculate diameter, circumference, circle area, sector area and arc length.
Formula / method
C=2πr; A=πr²; sector=(θ/360)πr²; arc=(θ/360)2πr.
How to use
Use dimensions from the same unit system and identify whether values are radius, diameter, height, side length or slant height.
What this calculator answers
The Circle Calculator uses the requested values to calculate the requested result. The core method is C=2πr; A=πr²; sector=(θ/360)πr²; arc=(θ/360)2πr.. This makes the assumptions visible so you can check whether the inputs match your situation.
How to get a useful result
Use dimensions from the same unit system and identify whether values are radius, diameter, height, side length or slant height.
How to interpret it
Geometric results assume the ideal shape described by the formula; real objects may require tolerances or waste allowances.
Before relying on the number
Recheck unusual inputs, confirm units and compare the result with any official quote, statement, specification or rule that applies to the real decision. Small changes in rates, time periods or measurements can materially change some results.