Triangle Area Calculator
Three Methods, Instant Results ⚡
Calculate the area of any triangle using three different methods. Choose whichever values you know.
Quick Examples
Triangle Area Formulas
Base & Height: A = ½ × base × height
Heron's Formula (3 sides): A = √(s(s−a)(s−b)(s−c)) where s = (a+b+c) ÷ 2
Two sides & angle: A = ½ × a × b × sin(C)
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Frequently Asked Questions
Does the height have to be perpendicular?
Yes — the height used in the base × height formula must be the perpendicular height (at 90° to the base), not the length of a slanted side. If you only know the three sides, use Heron's formula instead.
What is Heron's formula?
Heron's formula calculates triangle area using only the three side lengths. It first finds the semi-perimeter s = (a+b+c) ÷ 2, then uses A = √(s(s−a)(s−b)(s−c)).
What is an included angle?
The included angle is the angle between the two sides you are using. If sides a and b meet at angle C, then A = ½ × a × b × sin(C).