how to find height of a triangle

If you are looking for an easy tool to calculate the height in any triangle, you're in the right place - this triangle height calculator is the tool for you. Whether you are looking for the triangle height formulas for special triangles such as right, equilateral or isosceles triangle or any scalene triangle, this calculator is a safe bet - it can calculate the heights of the triangle, as well as triangle sides, angles, perimeter and area. Don't wait any longer, give it a go!

If you are still wondering how to find the height of an equilateral triangle or what's the formula for height without a given area, keep scrolling and you'll find the answer.

What is the altitude of a triangle?

Every side of the triangle can be a base, and from every vertex you can draw the line perpendicular to a line containing the base - that's the height of the triangle. Every triangle has three heights, which are also called altitudes. Drawing the height is known as dropping the altitude at that vertex.

height of a triangle - altitude of a triangle

How to find the height of a triangle - formulas

There are many ways to find the height of the triangle. The most popular one is the one using triangle area, but many other formulas exist:

Given triangle area

Well-known equation for area of a triangle may be transformed into formula for altitude of a right triangle:

area = b * h / 2, where b is a base, h - height
so h = 2 * area / b

But how to find the height of a triangle without area? The most popular formulas are:

Given triangle sides

It's using an equation called Heron's formula that lets you calculate the area if given sides of the triangle. Then, once you know the area, you can use the basic equation to find out what is the altitude of a triangle:

Heron's formula: area = 0.25 * √((a + b + c) * (-a + b + c) * (a - b + c) * (a + b - c))
so h = 0.5 * √((a + b + c) * (-a + b + c) * (a - b + c) * (a + b - c)) / b

Given two sides and the angle between

Use trigonometry or another formula for the area of a triangle:

area = 0.5 * a * b * sin(γ)
(or area = 0.5 * a * c * sin(β) or area = 0.5 * b * c * sin(α) if you have different sides given)
h = 2 * 0.5 * a * b * sin(γ) / b = a * sin(γ)

If your shape is a special triangle type, scroll down to find the height of a triangle formulas. Simplified versions of the general equations are easier to remember and calculate.

How to find the height of an equilateral triangle

An equilateral triangle is a triangle with all three sides equal and all three angles equal to 60°. All three heights have the same length that may be calculated from:

h△ = a * √3 / 2, where a is a side of the triangle

In an equilateral triangle the altitudes, the angle bisectors, the perpendicular bisectors and the medians coincide.

How to find the height of an isosceles triangle

An isosceles triangle is a triangle with two sides of equal length. There are two different heights of an isosceles triangle; the formula for the one from the apex is:

hᵇ = √(a² - (0.5 * b)²), where a is a leg of the triangle and b a base. The formula is derived from Pythagorean theorem
The heights from base vertices may be calculated from e.g.
- area formula: hᵃ = 2 * area / a = √(a² - (0.5 * b)²) * b / a
- trigonometry: hᵃ = b * sin(β)

How to find the altitude of a right triangle

A right triangle is a triangle with one angle equal to 90°. Two heights are easy to find, as the legs are perpendicular: if the shorter leg is a base, then the longer leg is the altitude (and the other way round). The third altitude of a triangle may be calculated from the formula:

hᶜ = area * 2 / c = a * b / c

How to find the altitude of the triangle with this triangle height calculator?

After reading our explanation, we're pretty sure that now you understand how to find the height of a triangle without the area given or what is the altitude of a triangle. But let's look at the simple example, to show you the flexibility of our tool:

Choose the triangle type. Assume we want to calculate the heights of a scalene triangle, so we don't change the default option.
Enter the given values. It could be three sides or two sides and an angle, let's stay with the first option: a = 6 in, b = 14 in, c = 17 in.
Triangle height calculator displayed all three heights - they are equal to 13.17 in, 5.644 in and 4.648 in. What is more, the calculator showed us all triangle angles, area and perimeter. That's awesome!

Hanna Pamuła , PhD candidate

Triangle with heights, sides and angles