Circle Calculator
Calculate area, circumference and diameter from radius.
About this tool
Calculate a circle's area, circumference and diameter from its radius, using \u03c0 (pi).
Key Features
- Area, circumference and diameter at once
- Works with any radius value
- Uses the precise value of \u03c0
How to Use
- Enter the circle's radius.
- Click Calculate.
Benefits
- Check geometry homework
- Plan circular layouts, gardens or designs
- Quick reference without remembering the formulas
Frequently Asked Questions
Divide the diameter by 2 to get the radius, then enter that \u2014 radius is always half the diameter.
Area = \u03c0r\u00b2, and circumference = 2\u03c0r, where r is the radius. Diameter is simply 2r.