Circle Calculator
Enter a radius and instantly get every property of the circle: diameter, circumference and area, each computed from π with the full substituted formula shown step by step.
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TheCalculators — Circle Calculator
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Circle Area
78.539816 units²
r = 5 · A = πr² = π × 5²
- Radius
- 5 units
- Diameter
- 10 units
- Circumference
- 31.415927 units
- Area
- 78.539816 units²
- π used
- 3.1415926535
Circle properties
Step-by-step
- 1Diameterd = 2r = 2 × 5 = 10 units
- 2CircumferenceC = 2πr = 2 × π × 5 = 31.415927 units
- 3AreaA = πr² = π × 5² = π × 25 = 78.539816 units²
Most useful next
Formula
d = 2r · C = 2πr · A = πr²
Pro tips
- • Circumference ÷ diameter equals π for every circle, no matter the size.
- • If you know the diameter instead, halve it before entering — or enter d/2 directly.
- • Area grows with the square of radius: tripling r makes the area 9× larger.
FAQ
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