# What is the area of a circle with diameter 12 kilometers?

Here is the answer to questions like: how to find the area of a circle with diameter 12 kilometers?

Use the this circle area calculator below to find the area of a circle given its diameter, 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

## 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 diameter

### 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 square centimeters (cmÂ²), if in inches, will get the answer in square inches (inÂ²) and so on ...

Circumference is often misspeled as circunference.

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

## Sample Circle Area Calculations

- Area of a Circle with radius 21 yard
- Area of a Circle with circumference 11.9 mm
- Area of a Circle with diameter 2.4 units
- Area of a Circle with circumference 12.1 kilometers
- Area of a Circle with diameter 22 meters
- Area of a Circle with diameter 18.4 kilometers
- Area of a Circle with circumference 26.69 yard
- Area of a Circle with diameter 4 miles
- Area of a Circle with diameter 73 centimeters
- Area of a Circle with circumference 16.8 mm

- Area of a Circle with circumference 10.5 units
- Area of a Circle with radius 9.8
- Area of a Circle with diameter 14.4 feet
- Area of a Circle with radius 19.8 meters
- Area of a Circle with circumference 2 pi centimeters
- Area of a Circle with radius 4.7 yard
- Area of a Circle with radius 82 miles
- Area of a Circle with circumference 18 pi centimeters
- Area of a Circle with circumference 13.7 feet
- Area of a Circle with circumference 1.8 centimeters

- Area of a Circle with diameter 6.5 feet
- Area of a Circle with diameter 84 kilometers
- Area of a Circle with radius 8.2 inches
- Area of a Circle with radius 67 feet
- Area of a Circle with radius 2228 centimeters
- Area of a Circle with radius 3.1 inches
- Area of a Circle with diameter 71 inches
- Area of a Circle with diameter 28 feet
- Area of a Circle with circumference 6.6 inches
- Area of a Circle with diameter 11.3 feet