The circle does not have angles and straight sides, so calculating the area of this geometric figure was not an easy task. But ancient scientists coped with this task and invented all possible formulas. You do not need to remember them, because you can use our simple, fast and handy online circle area calculator. Why not bookmark this page for your browser?

## Formulas for calculating the area of a circle

Depending on the initial data, there are three basic formulas. We use them.

- If you know the radius:
**S = πR²**, where R is the radius, π = 3.1415. - If you know the diameter:
**S = 0.25πD²**, where D is the diameter, π = 3.1415. - If you know the circumference:
**S = L² / 4π**, where L is the circumference, π = 3.1415.

## Can I use these formulas in everyday life?

Of course! Measure the diameter of the cup and calculate the bottom area. Measure the radius of the wheel of your car and you will know its area for painting. Measure the area of the moon in the sky, multiply by the speed of light, divide by the age of the universe. It will be fun!

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