Area of a Circle (In Steps)

Learning Objectives Define radius, diameter, and pi. State the formula for the area of a circle: A = πr². Calculate the area of a circle when given the radius. Calculate the area of a circle when given the diameter by first finding the radius. Use approximations for pi (like 3.14 or 22/7) to find the area. Solve real-world problems involving the area of a circle and include appropriate square units in their answers. Have you ever wondered which pizza is a better deal, a 12-inch medium or two 8-inch smalls? 🍕 Let's find out how to calculate the space on top! In this tutorial, you will learn the step-by-step process for calculating the area of any circle. Understanding this formula is key to measuring the two-dimensional space inside a circular shape, a skill used in de...

TermDefinitionExample CircleA two-dimensional shape made up of all points that are the same distance from a central point.A bicycle wheel, a coin, or the face of a clock. Radius (r)The distance from the center of a circle to any point on its edge.If a circle has a line drawn from its center to its edge that measures 5 cm, the radius is 5 cm. Diameter (d)The distance across a circle passing through its center. The diameter is always twice the length of the radius (d = 2r).If a pizza measures 14 inches from one side to the other through the middle, its diameter is 14 inches. Pi (π)A special, non-repeating number that represents the ratio of a circle's circumference to its diameter. For calculations, we often use the approximations 3.14 or 22/7.π ≈ 3.14159... AreaThe measure of the spac...

Area of a Circle Formula A = \pi r^2 This is the primary formula for finding the area (A) of a circle. It means you multiply pi (π) by the radius (r) squared (r × r). Radius from Diameter Formula r = d / 2 Use this formula when you are given the diameter (d) but need the radius (r) for the area formula. Simply divide the diameter by 2.