Triangle Area Calculator

Calculate the area of a triangle from its base and height, or all three sides using Heron's formula.

Given values

Base

Height

Side a

Side b

Side c

Area

Last updated: 2026-08-30

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FAQ

What is Heron's formula?

With semi-perimeter s = (a+b+c)/2, the area equals √(s(s−a)(s−b)(s−c)). It works from side lengths alone, no height needed.

When is a triangle impossible?

When any side is longer than the sum of the other two — the triangle inequality fails and Heron's formula returns a negative value under the root.

How do I find the area without knowing the height?

Use Heron's formula from the three sides: s = (a+b+c)/2, then area = √(s(s−a)(s−b)(s−c)).

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