Triangle Perimeter Calculator
P = a + b + c. Sum of all three sides.
Result
Perimeter
18.0000
Scalene; area (Heron) ≈ 14.6969.
- Side a5
- Side b6
- Side c7
- Perimeter18.000000
- Triangle?Yes
- TypeScalene
- Area (Heron)14.696938
Step-by-step
- P = a + b + c = 5 + 6 + 7 = 18.0000.
- Heron: s = P/2 = 9.0000. Area = √(s(s−a)(s−b)(s−c)) = 14.6969.
How to use this calculator
- Enter three side lengths.
- Calc verifies triangle inequality.
- Reads perimeter + area + type.
About this calculator
Triangle perimeter is just the sum of three sides. The triangle inequality requires each side < sum of the other two — otherwise it's not a real triangle. Heron's formula gives area from sides only: Area = √(s(s−a)(s−b)(s−c)) where s = P/2 is the semi-perimeter. Equilateral (all equal), isosceles (two equal), scalene (all different) classify by side equality.
Frequently asked
Each side < sum of the other two. 3-4-5: valid. 1-2-5: invalid (1+2 < 5).
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