Triangle Area Calculator
Three ways to get the area — base–height, three sides (Heron), or SAS with the included angle.
Which Method Should I Use?
Use base–height when an altitude is known; Heron's formula when only the three side lengths are known; and the SAS formula (½·a·b·sin C) when you have two sides and the angle between them. All three give the same area for the same triangle.
Frequently Asked Questions
What units does the answer use?
Whatever units you enter, squared — inches give square inches, cm give cm².
Why does Heron need the triangle inequality?
If one side is longer than the other two combined, no triangle exists and the square root would be of a negative number.
Does the SAS angle need to be the included angle?
Yes — C must sit between sides a and b, or the formula measures a different triangle.