Area of a Circle Calculator

Use the this circle area calculator below to find the area of a circle given its radius, or other parameters. To calculate the area, you just need to enter a positive numeric value in one of the 3 fields of the calculator. You can also see at the bottom of the calculator, the step-by-step solution.

Area of a Circle Calculator

Formulas:

Circle area formula

Inputs:

or
or

Result:

The area of a circle with radius 5 is 78.539816339745

Solution Steps:

Area of a cicle in terms of radius:

Area = π . r2 = 3.14 . 52 = 78.54 .

In terms of diameter:

Area = π . (d/2)2 = 3.14 . (10/2)2 = 3.14 . (5)2 = 78.54 .

In terms of circumference:

Area = C2/(4π) = 31.422/ = 986.96/(4 . 3.14) = 986.96/(12.56) = 78.54 .

Note: for simplicity, some results may be rounded to nearest hundredth and π was rounded to 3.14. See formula details below in this page.

Formula for area of a circle

Here a three ways to find the area of a circle (formulas):

Circle area formula in terms of radius

Circle area formula in terms of radius

Circle area formula in terms of diameter

Circle area formula in terms of diameter

Circle area formula in terms of circumference

Circle area formula in terms of circumference

See below some definitions related to the formulas:

Circumference

Circumference is the linear distance around the circle edge.

Radius

The radius of a circle is any of the line segments from its center to its perimeter. The radius is half the diameter or r = d/2.

Diameter

The diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints lie on the circle. The diameter is twice the radius or d = 2r.

The Greek letter π

π represents the number Pi which is defined as the ratio of the circumference of a circle to its diameter or π = C / d. For simplicity, you can use Pi = 3.14 or Pi = 3.1415. Pi is an irrational number. The first 100 digits of Pi are: 3.1415926535 8979323846 2643383279 5028841971 6939937510 5820974944 5923078164 0628620899 8628034825 3421170679 ...

Note:

If you input the radius in centimeters, you will get the answer in squere centimeters (cm²), if in inches, will get the answer in square inches (in²) and so on ...

Circumference is often misspeled as circunference.

You can use our area unit converter to see the results in other units.

Disclaimer

While every effort is made to ensure the accuracy of the information provided on this website, we offer no warranties in relation to these informations.