Circle Area Calculator
Area, circumference and diameter of a circle from its radius.
Results
Area
19.635
m²
Circumference
15.708
m
Diameter
5
m
What this tool does
Everything about a circle follows from one measurement. Give the radius and you get the area, the distance around the edge and the diameter; if you only know the diameter, halve it first. The units shown are metres, but any consistent unit works — enter centimetres and the area comes out in square centimetres.
Formula
A = π × r² , C = 2 × π × r
Variables
| Symbol | Meaning | Unit |
|---|---|---|
r | Radius | m |
A | Area | m² |
C | Circumference | m |
d | Diameter | m |
Worked example
- Radius2.5 m
- Area19.635 m²
- Circumference15.708 m
- Diameter5 m
Limitations
- Mixing units is the most common source of error. Convert every input to the units shown next to each field before calculating.