Important Geometry Formulas

Choose from one of the many geometry formulas listed here, or scroll through to find the one you are looking for.

Areas:  Triangle, Rectangle, Parallelogram, Trapezoid, Circle, Regular

Volume:  Prism, Cylinder, Pyramid, Cone, Sphere

Right Triangles: Trig ,Pythagorean Theorem, 45-45-90, 30-60-90

Coordinate Geometry:  Distance, Midpoint, Slope

Areas of Two Dimensional Figures

Triangle:  A three sided figure.

Rectangle:  A quadrilateral with four right angles.

Parallelogram:  A quadrilateral with two pairs of opposite sides parallel.

Trapezoid:  A quadrilateral with exactly one pair of opposite sides parallel.

Circle:  A set of points all equidistant from a given point - the center.

Any Regular Polygon:  A figure with all sides and angles congruent.

Volume and Surface Area of Three Dimensional Figures

Formulas for Right Triangles

In the figure below, side lengths a and b are the legs of the triangle, and c is the hypotenuse.  *Remember, the hypotenuse is always across from the right angle.

For the special right triangles, the side lengths are always in the proportions shown.

Geometry Formulas for Coordinate Geometry

The formulas shown below are to be used on the coordinate plane.  The first point is given as (x₁, y₁) and the second point is (x₂, y₂).  For your problem, it does NOT matter which point you name "first" and which point you name "second."

Didn't find one of the geometry formulas that you were looking for?  Contact us to make a request!  Don't forget to browse our library of free geometry worksheets so that you can practice using all of these formulas.

For more Grade A help in geometry, view the free geometry help page, and head over to the Grade A Home Page.