Triangle Area Calculator (3 methods)
Base × height, Heron's formula (SSS), or side-angle-side (SAS) — pick the inputs you have.
Result
General calculation reads
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How to use this calculator
- Pick the method that matches your inputs.
- Base+height: orthogonal height to the base (drop a perpendicular if needed).
- SSS (Heron): three side lengths.
- SAS: two sides and the angle BETWEEN them (not opposite).
About this calculator
Triangle area has three classic formulas depending on what you can measure. Base × height (½·b·h) is the textbook formula but requires knowing the perpendicular height. Heron's formula (named after Hero of Alexandria, ~60 AD) gives the area from just the three side lengths via the semi-perimeter: A = √(s(s−a)(s−b)(s−c)) where s = (a+b+c)/2. Side-Angle-Side (SAS) uses two sides and the included angle: A = ½·a·b·sin(C) — useful in surveying and trigonometry where one angle is known. All three give identical results for a valid triangle; pick the one whose inputs match your situation. Triangle inequality check: the longest side must be less than the sum of the other two — the tool flags violations explicitly.
Frequently asked
Why is Heron's formula useful?+
What's the triangle inequality?+
Source?+
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