Math Calculators

Isosceles Triangle Calculator

Calculate the height, area, perimeter and base angles of an isosceles triangle from its base and equal legs, each in the unit of your choice.

Height —

Area —

Perimeter —

Base angle —

About the Isosceles Triangle Calculator

An isosceles triangle has two equal legs and a base. Dropping a perpendicular from the apex to the base creates two congruent right triangles, which is the key to finding its height and angles. The base and leg each have their own unit selector, and so does every length and area result, so you can mix units freely.

Formula: Height = √(leg² − (base/2)²) · Area = ½ × base × height · Base angle = arccos((base/2) ÷ leg)