Geometry Formulas

There are many geometry formulas you will use during your time studying geometry. GradeA presents clear graphics and explanations to help you understand all of these formulas..

Please select from the quick links below, or feel free to scroll through the page to look at all of the formulas.


Right Triangles:

Coordinate Geometry:



For a comprehensive formula sheet that is perfect store in your website, view this website's geometry formulas. Perfect for your notebook!

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.

Area of a parallelgram formula








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

Area of a trapezoid formula

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

Area of a circle formula

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

Area of a regular polygon formula


Formulas for Right Triangles

Pythagorean Theorem:

The most common formula for right triangles is Pythagorean theoreamn. You probably have heard of this one before: a2 + b2 = c2

For more details, read visit our pythagorean theorem page, or visit our biography of pythagoras, the man credited with the discovery of the famous formula.



Many geometry students begin to learn the trigonometric functions towards the end of the course. You probably are only going to use the first three functions, sin, cos, and tan, but we listed all 6 just in case.

For a lot more details about trigonometry, visit GradeA's trigonometry page.

Trigonometry formulas

Special right triangle have side lengths that always remain in proportion. So unlike with the pythagorean theorem where you need to know two side lengths to find the third, in this case you only need to know one side lengh in order to find the other two.

45-45-90 Special Right Triangle:

45-45-90 right triangle formula

Visit GradeA's 45-45-90 right triangle page.

30-60-90 Special Right Triangle :

Visit GradeA's 30-60-90 right triangle page.


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."

Additional Information

If you did not find one of the formulas that you were looking for, please view these additional geometry formulas. You can download a .printable formula sheet that covers everything you will need to know in geometry

You may also want to view our free geometry help page for additional geometry resources, or you can visit the GradeA homepage for even more free math help resources.

As always, they are GradeA!



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