Area and perimeter

This course is a part of Basic geometry, a 8-course Topic series from Khan Academy.

Area and perimeter help us measure the size of 2D shapes. We’ll start with the area and perimeter of rectangles. From there, we’ll tackle trickier shapes, such as triangles and circles.

This course contains 7 segments:

Count unit squares to find area

Find area of shapes by counting unit squares. Some shapes will require combining partial square units to find area. Create rectangles with a given area by covering unit squares.

Area of rectangles

Transition from counting unit squares to multiplying side length to find area. Measure side lengths with a ruler to find area. Find area of rectangles by multiplying side lengths. Find a missing side length of a rectangle when given the other side length and area.

Perimeter

Have you ever wondered how much fencing you need to surround a plot of land? No? Well, you should still go through this tutorial just in case. You'll learn what perimeter is and how to calculate it.

Area of parallelograms

Understand the formula for the area of a parallelogram.

Area of triangles

Understand the formula for the area of a triangle.

Area of trapezoids & composite figures

Finding the area of more complex shapes like trapezoids and composite figures (shapes built from other shapes)

Area and circumference of circles

A circle is at the foundation of geometry, and at the foundation of a circle is a special number called Pi. This number allows us to relate the radius, diameter, and circumference of a circle.