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:


where p is half the perimeter, or

Try this Drag the orange dots to reshape the triangle. The formula shown will recalculate 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 higherorder polygons.
Calculator
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.
Other triangle topics
General
Perimeter / Area
Triangle types
Triangle centers
Congruence and Similarity
Solving triangles
Triangle quizzes and exercises
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