What you provide
What you provide
- Side a: First triangle side length.
- Side b: Second triangle side length.
- Side c: Third triangle side length.
GEOMETRY / THREE SIDES
Triangle Calculator
Calculate triangle area with Heron’s formula plus perimeter and semiperimeter from three valid side lengths.
- 01 Calculated in this tab
- 02 Values stay in this browser tab
- 03 Use boundary
Use boundary
Calculation path
Triangle inequality is validated before Heron’s formula uses the semiperimeter to calculate area.
Calculation path
s = (a + b + c) / 2; area = sqrt(s(s-a)(s-b)(s-c)).
What you receive
What you receive
- Triangle area
- Perimeter and semiperimeter
- Longest side
Use boundary
Choose the maximum decimal places shown. This does not increase source accuracy.
The three lengths must form a non-degenerate triangle and use the same unit; this tool does not infer angles.
Results are educational math aids. Check notation, units, rounding, assumptions, and required precision before using an answer in graded, engineering, financial, or safety-critical work.