Circle calculator
Find a circle’s area, circumference and diameter from its radius.
Formula
A = πr²; C = 2πr; d = 2r; radius converted to meters
Radius: 1 m · Area ≈ pi×(1 m)^2 · Circumference ≈ 2×pi×(1 m) · Diameter ≈ 2×(1 m)
How to use
- Enter the radius.
- Choose its length unit.
- Read area, circumference and diameter.
Examples
- Radius 1 m gives area approximately 3.141593 m².
- Radius 5 m gives diameter 10 m.
Frequently asked questions
Is radius half the diameter?
Yes. If you know the diameter, divide it by two before entering it.
Why is area in square meters?
The radius is converted to meters, then squared in the area formula.
Is π taken as 3.14?
No. It uses π to full calculator precision, then rounds the displayed result.
Sources
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