Triangle Area (Base × Height) Calculator
Find the area of a triangle from its base and perpendicular height using A = ½ × base × height, the simplest triangle-area formula.
How it works
A = ½ · b · h · where b = base, h = perpendicular height
Every triangle is exactly half of the parallelogram built on the same base and height, which is why the area is ½ · base · height. The height must be measured perpendicular to the chosen base, not along a slanted side. Any of the three sides can serve as the base as long as you use the matching perpendicular height — the answer is the same.
Worked example
For a triangle with a base of 10 units and a perpendicular height of 6 units, A = ½ · 10 · 6 = ½ · 60 = 30 square units.
Sources: Triangle — Wikipedia
Frequently asked questions
Does it matter which side I call the base?
No. Any of the three sides can be the base, provided you pair it with the perpendicular height drawn to that side. All three base–height pairs give the identical area.
What if I only know the three side lengths?
Use Heron’s formula instead, which finds the area from the three sides without needing a height. This calculator needs a base and its perpendicular height.
Is the slant side the same as the height?
Only in a right triangle where a leg is perpendicular to the base. In general the height is shorter than the slanted side, because it is the straight perpendicular distance to the opposite vertex.
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This calculator is for educational purposes. Double-check important results before acting on them.