Heron's Formula for the area of a triangle(Hero's Formula)
A method for calculating the area of a triangle when you know the lengths of all three sides.

Let a,b,c be the lengths of the sides of a triangle. The area is given by:
herons formula
where p is half the perimeter, or herons formula
Try this Drag the orange dots to reshape the triangle. The formula shown will re-calculate the triangle's area using Heron's Formula

Heron was one of the great mathematicians of antiquity and came up with this formula sometime in the first century BC, although it may have been known earlier. He also extended it to the area of quadrilaterals and higher-order polygons.


Side 1 clear
Side 2 clear
Side 3 clear

Use the calculator on the right to calculate the area of a triangle given 3 sides using Heron's formula.

Enter the three side lengths and press 'Calculate'. The area will be calculated.

Related triangle topics


Perimeter / Area

Triangle types

Triangle centers

Congruence and Similarity

Solving triangles

Triangle quizzes and exercises


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