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Triangle Calculator

Solve any triangle from three sides (SSS): area with Heron’s formula, perimeter, angles, heights and triangle type.

Enter values

Results update as you type.

Result

Area

14.696938

Perimeter
18
Angle A
44.4153 °
Angle B
57.1217 °
Angle C
78.463 °
Height to side a
5.878775
Type
Scalene, acute
Step-by-stepShow
  1. s = (5 + 6 + 7) ÷ 2 = 9
  2. Area = √(s(s−a)(s−b)(s−c)) = 14.696938

About the Triangle Calculator

Solve any triangle from three sides (SSS): area with Heron’s formula, perimeter, angles, heights and triangle type.

Also known as: triangle area calculator, herons formula calculator, triangle solver, area of triangle, triangle angles, triangle area.

How to use this calculator

  1. Enter side a, side b, side c.
  2. The result updates instantly as you type — press Calculate (or Enter) at any time.
  3. Open “Step-by-step” to see how the answer was worked out.
  4. Use Copy result or Share to save the answer or send a link with your inputs.

Formula

Area = √(s(s − a)(s − b)(s − c)), s = (a + b + c)/2

Worked example

Using the values pre-filled in the calculator above:

  • Side a = 5
  • Side b = 6
  • Side c = 7

the calculator returns:

  • Area: 14.696938
  • Perimeter: 18
  • Angle A: 44.4153 °
  • Angle B: 57.1217 °

Working

  1. s = (5 + 6 + 7) ÷ 2 = 9
  2. Area = √(s(s−a)(s−b)(s−c)) = 14.696938

Frequently asked questions

How do I find the area with base and height?

Area = ½ × base × height. Use the triangle area calculator for that method, or enter all three sides here to use Heron’s formula.