What you provide
What you provide
- Circle radius: Distance from the center to the edge.
- Input context: keep the entered value and every interpreted output in one consistent numeric or measurement system.
GEOMETRY / ROUND SHAPES
Circle Calculator
Calculate circle area, circumference, and diameter from one positive radius in any consistent length unit.
- 01 Calculated in this tab
- 02 Values stay in this browser tab
- 03 Use boundary
Use boundary
Calculation path
The radius is squared for area and doubled for diameter; pi connects radius to area and circumference.
Calculation path
Area = pi x radius^2; circumference = 2 x pi x radius.
What you receive
What you receive
- Circle area
- Circumference
- Diameter and radius recap
Use boundary
Choose the maximum decimal places shown. This does not increase source accuracy.
Outputs use generic units; area is in squared units and all linear results retain the radius input unit.
Results are educational math aids. Check notation, units, rounding, assumptions, and required precision before using an answer in graded, engineering, financial, or safety-critical work.