Area of a circle calculator.

You need to know circle's radius or diameter for you will be able to calculate it's area. If you have one of mentioned values it won't be a problem to calculate the area.
Сircle's area is calculated by the next formulas:

1. If you know the radius:
   S=πR²
2. If you know the diameter:
   S=πD²/4

where S – area, R – radius, D – diameter, π – pi constant which equal about 3,14.