Geometry Formulas

Area, perimeter, and the shapes you meet every day.

• Area of a Circle - The area of a circle is pi times the radius squared. See what the formula means, why it works, worked examples, and free practice.
• Area of a Parallelogram - The area of a parallelogram is base times height. See what the formula means, why it works, worked examples, and free practice.
• Area of a Rectangle - The area of a rectangle is length times width. See what it means, why it works by counting squares, worked examples, and free practice.
• Area of a Trapezoid - The area of a trapezoid is one half the sum of the parallel sides times the height. See what it means, why it works, worked examples, and free practice.
• Area of a Triangle - The area of a triangle is half the base times the height. See what base and height mean, why the half is there, worked examples, and free practice.
• Circumference of a Circle - The circumference of a circle is pi times the diameter, or two times pi times the radius. See what it means, why pi appears, and free practice.
• Perimeter Formulas - Perimeter is the total distance around a shape. See the square, rectangle, and triangle formulas, why they work, worked examples, and free practice.
• The Pythagorean Theorem - The Pythagorean theorem says a squared plus b squared equals c squared for a right triangle. See what it means, why it works, worked examples, and free practice.