Circle Calculator
Find circle area, circumference, diameter or radius. Free online Circle Calculator for geometry — instant, accurate results, mobile-friendly, no signup needed.
Derivation
- ├── 01Given
r = 5 - ├── 02Formula
Area = π·r² · Circumference = 2π·r · Diameter = 2r - ├── 03r²
5 × 5 = 25.0000 - ├── 04Substitute
π × 25.0000 = 78.5398 - ├── 05Area78.5398
- ├── 06Circumference2π × 5 = 31.4159
- └── 07Diameter2 × 5 = 10.0000
Archimedes (c. 250 BCE) estimated π between 223⁄71 and 22⁄7 by inscribing and circumscribing 96-sided polygons in a circle.
Understanding the Circle Calculator
The Circle Calculator helps you compute find circle area, circumference, diameter or radius.. It runs entirely in your browser with no sign-up required.
Geometry is what turns raw measurements into useful answers about space — how much paint, how big a yard, how much material a project will need. Every craftsperson, architect, and DIYer reaches for these formulas regularly. The Circle Calculator sits in that toolkit — it find circle area, circumference, diameter or radius. Enter your numbers above and the result updates instantly; every step of the math is shown in the Derivation panel so you can see exactly how the answer was reached.
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