Geometry can be confusing between calculating area, volume, circumference and all the other things you’re expected to know. The formulas can get jumbled in your head. However, being able to calculate the area of a circle is one of the basic formulas for geometry and not a hard one to master.

### Calculating a Circle's Area

Understand the type of measurement you are seeking. There are three types of geometry measurement you may make. These are linear, area and volume measurements. They are easy to distinguish from each other. Volume measurements will have a final answer that is cubed, such as cube feet. An area measurement will have a final answer that is squared, such as square inches. Linear measurements will have no exponents with their units in the final answer. Since we are seeking square feet, you know that we are seeking the area of a circle.

Write the formula down. The formula for finding the area in a circle is: ?r2. To understand what the formula means, you need to understand what the variables are. ? is 3.14 (22/7). It’s a universal constant that shows up naturally in many things. The second variable is r, which stands for radius. This is the measurement from the center of the circle to the edge.

Take your measurement. Since you want to have an answer in square feet, you need to use feet as your basic unit for measurement. This means when you measure the radius of your circle, you need to convert it to feet. For instance if your radius is 9 inches, you convert it to feet by dividing it by 12 because there are 12 inches in a foot. So your new radius measurement is .75 feet.

Calculate the area. Using the above example, we can calculate the area of a circle with a 9-inch radius. First, plug in the information: Area=?r2 or (3.14).75 ft2. This becomes 3.14 x (.75 ft x .75 ft) = 3.14 x .5625 ft2= 1.77 ft2.

#### Tip

Though the math is easy enough to do by hand, a calculator will make it go quicker.

#### Warning

Make sure the units in your answer are squared. Otherwise, you aren't talking about area.