Triangle Calculator
Area, perimeter and type from three sides (Heron's formula).
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About this calculator
Any three lengths satisfying triangle inequality define a unique triangle up to congruence — Heron's formula yields area without needing angles.
Formula
Heron: Area = √[s(s−a)(s−b)(s−c)], s = (a+b+c)/2.
Frequently Asked Questions
Right triangle check?
Sort sides: if a²+b² equals c² (within rounding), it's right-angled.