How many square inches in a 18 inch Dia. circle?

Answer 1

The formula for the area of a circle is A = PI R squared.

• Pi is about 3.1416

• R is the radius, half the diameter or 18/2 = 9

A= 3.1416 * 9 * 9 = 254.4696

Using more digits in PI will give slightly different answers such as

3.14159265359 * 9 * 9 = 254.469004941 which still is about the same value.

So the area of an an 8 inch diameter circle (rounded) is about 254.5 square inches