Triangle Calculator
Equilateral Triangle Calculator
An equilateral triangle has three equal sides and three 60° angles. Knowing one of its hei...
Read MoreRight Triangle Calculator
A right triangle has one 90° angle. Using the Pythagorean theorem, two known sides let you...
Read MoreAbout This Category
Two triangle pages cover the shapes that come up most: the equilateral triangle, where one side defines everything, and the right triangle, where two sides or one side and one angle define the rest.
The right-triangle page is the one to use for diagonals, screen sizes, roof slopes and distances, because it applies the Pythagorean theorem and basic trigonometry in both directions.
Frequently Asked Questions
How do I find the height of an equilateral triangle?
Multiply the side by √3/2. For a side of 10 that is 8.66; the area is then 43.3.
Which side is the hypotenuse?
The one opposite the right angle, and always the longest. In a 3-4-5 triangle it is 5, which is why that triple is used for checking square corners.
Do the angles have to be in degrees?
The trigonometric inputs are in degrees on these pages. Convert radians first: multiply by 180 and divide by π.
Calculators in This Category
Sources & last update
2026-10-19