⭕ Circle Area, Circumference & Diameter Calculator
Calculate circle area (A = πr²), circumference (C = 2πr), and diameter (d = 2r) instantly from any given radius input. 100% free.
Free No Signup Required Browser-Based
Total Circle Area (A = πr²)
78.5398
Circumference (C = 2πr): 31.4159 units
Circle Diameter (d = 2r)
10.00 unitsInput Radius (r)
5.00 unitsHow to Use Circle Area, Circumference & Diameter Calculator
- Input the radius of the circle
- Review total computed area in square units
- Inspect diameter and circumference values
📖 Technical Encyclopedia & Standards Reference
Calculate circle area (A = πr²), circumference (C = 2πr), and diameter (d = 2r) instantly from any given radius input. 100% free. This tool computes outputs according to official open technical and scientific specifications.
✓ Open Standards AlignmentCompliant with ISO/IEC, W3C, NIST, and standard mathematical formulations.
✓ 100% Client-Side / SecureZero server logging. Computations execute entirely in your local browser sandbox.
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Frequently Asked Questions
What is the formula for the area of a circle?
Area = π × r², where r is the radius of the circle and π is approximately 3.14159.
How are diameter and circumference related?
Diameter is twice the radius (d = 2r), and Circumference is π times the diameter (C = πd = 2πr).