Area and Perimeter Basics

Geometry · Axiom Academy

Two fundamental measurements of shapes — the distance around, and the space inside. Area and perimeter are everywhere. From the paint you need for a room, to the fence around a yard, to the size of a pizza, these two measurements let us describe and work with shapes in the real world. They answer two different questions about the very same shape. Watch one rectangle, 8 units by 5 units, answer both questions at once: a marker travels all the way around the border (that path length is the perimeter ), and the inside tiles in with unit squares (that count is the area ). Same shape, two answers: perimeter measures the trip around, area measures the space inside. Resize the rectangle and watch both change Drag the sliders to change the rectangle's width and height. The blue border is the perimeter; the purple squares are the area. Notice how the two totals move differently as the shape grows. Double both sides and the perimeter doubles, but the area quadruples — try sliding both to twice their size. Every shape has its own two answers Pick a shape to see how perimeter and area are found for each. Perimeter is always "add all the sides," but the area formula depends on the shape. Perimeter and area use different units — lengths (like cm) for perimeter, square units (like cm²) for area. Two measurements you'll use everywhere

This is the written version of the interactive lesson above. See the full Geometry course.