Triangle Area Calculator
Find a triangle's area from its base and height.
Result
Area
30.0000
How it works
The area of a triangle is half of base times height: A = (b × h)/2. The half is no mystery — every triangle is exactly half of a parallelogram cut along its diagonal, and the parallelogram's area is base × height. Any of the three sides may serve as the base; what matters is that the height is measured perpendicular to it, from the base line to the opposite vertex. In an obtuse triangle the foot of that height can fall outside the triangle — the formula still holds. With a base of 10 and height of 6, the area is 30. If you know the three sides but no height, use Heron's formula instead; if you know two sides and the angle between them, A = ½·a·b·sin(C) does the job.
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Frequently asked questions
What is the area formula for a triangle?
Area = (base × height) ÷ 2.
Which height do I use?
The perpendicular height from the base to the opposite vertex — not a slanted side.
What if I know the three sides but not the height?
Use Heron's formula: with s = (a+b+c)/2, the area is √(s(s−a)(s−b)(s−c)). No height needed — our Heron calculator does it directly.
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