⚡ Quick Answer
Circle formulas: Area = πr², Circumference = 2πr, Diameter = 2r. Given any one value, all others can be calculated. π ≈ 3.14159.
📂 Math
⭕ Circle Calculator
Calculate circle area, circumference, diameter, and radius from any single known value. Essential for geometry students and engineers.
✨ Your Result
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Fill in the values above and click Calculate ✨
✅ Trusted Tool
Uses standard geometric formulas. Free for students and professionals. No sign-up needed.
🤔 How Does This Work?
- Area = πr²
- Circumference = 2πr
- All values derived from whichever you provide
❓ Frequently Asked Questions
What is the formula for circle area?▼
Area = π × r², where r is the radius. If you know the diameter, radius = diameter/2.
What is the difference between radius and diameter?▼
Radius is the distance from center to edge. Diameter is the distance across through the center — exactly twice the radius.