Three ways to measure a triangle
The simplest triangle area is half the base times the height. When you don't know the height but do know all three side lengths, Heron's formula gives the area from the sides alone. And for a right-angled triangle, Pythagoras' theorem links the two shorter sides to the hypotenuse: a² + b² = c². This calculator handles all three, and checks that three sides can actually form a triangle.
Frequently asked questions
How do I find a triangle's area without the height?
Use the three-sides method. Heron's formula works out the area from the side lengths, no height needed.
What is Pythagoras' theorem?
In a right triangle, the square of the hypotenuse equals the sum of the squares of the other two sides: a² + b² = c².
Why does it say "not a valid triangle"?
Three lengths only form a triangle if each side is shorter than the sum of the other two. If not, no triangle exists.