Circle Area Calculator
Filling In the Circle
Every circle's area scales with the square of its radius, tied together by the constant π — the ratio, unchanging since antiquity, between a circle's circumference and its diameter. Double the radius and the area quadruples; that squared relationship is what makes circle area a slightly different kind of calculation than the straight-line scaling of a circumference.
The Formula
Area = πr²
Area by Radius
| Radius | Area |
|---|---|
| 1 | 3.1416 |
| 2 | 12.5664 |
| 3 | 28.2743 |
| 5 | 78.5398 |
| 10 | 314.1593 |
Values use π ≈ 3.14159265; results are rounded to 4 decimal places.
Where This Matters
- Material and coverage estimates — sizing a circular tabletop, pool cover, or lawn sprinkler's coverage area.
- Pipe and duct sizing — cross-sectional area drives flow capacity calculations in plumbing and HVAC work.
- Manufacturing — calculating raw material needed to stamp or cut circular blanks.
How to Use This Calculator
- Enter the circle's Radius.
- Select Calculate to get the area.
Related Calculations
Need the distance around instead? Use the Circle Circumference Calculator, or move into three dimensions with the Sphere Volume Calculator.