🔺 Heron’s Formula Calculator
Find the area of any triangle from just its three side lengths using Heron’s formula.
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What Heron’s formula does
Heron’s formula finds the area of a triangle using only its three side lengths, with no need to measure any angle. It first computes the semi-perimeter s = (a + b + c) / 2, then the area equals √(s(s-a)(s-b)(s-c)).
How to use this calculator
Enter the lengths of all three sides in the same unit. The calculator checks that the three lengths can actually form a triangle (each side must be shorter than the sum of the other two) before computing the area and perimeter.
If the sides you entered cannot form a valid triangle, the area will show as zero and the “Valid Triangle” indicator will read 0. This tool is for general math and educational use.
Last reviewed August 2026