How this calculator works
Calculate circle circumference, diameter, and area from radius in one step.
Formula
circumference = 2 * pi * r, area = pi * r^2, diameter = 2 * r
Step-by-step
- Enter the circle radius.
- Click Calculate.
- Read circumference, diameter, and area together.
Example
- Radius = 5
Circumference ≈ 31.4159, Area ≈ 78.5398
FAQs
What if I only know diameter?
Divide diameter by 2 to get radius, then calculate.
What unit is returned?
Results are in the same unit system as your radius input (for example cm, m, in, ft).