How triangle from three sides works
Check the triangle inequality, then find perimeter and area.
Formula and convention
Heron area = sqrt(s(s-a)(s-b)(s-c)), where s is half the perimeter.A worked example
Sides 3, 4, and 5 give perimeter 12 and area 6.
Scope and precision
Use the same unit for all sides. Each pair must sum to more than the third side. Collinear and impossible triangles are rejected.
Displayed results may be rounded. Inputs are processed locally and are not stored by this site. Keep the original values if you need to reproduce the result.
Why might another tool give a different result?
Compare unit definitions, rounding, period assumptions, and input values. This page states the convention used by this calculator.