Math

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Heron's Formula Calculator.

Calculate triangle area from three side lengths.

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Set your values

Results update as you type.

Result: area: 6.000000 · semiperimeter: 6.000000

Result

area: 6.000000 · semiperimeter: 6.000000

Use Cases

Geometry homework and exams

Quickly verify area calculations for triangles in math assignments, saving time and reducing errors.

Example: Check the area of a triangle with sides 5, 6, and 7 units.

Construction and land measurement

Estimate the area of triangular plots or spaces when only side lengths are known, useful for planning materials or layouts.

Example: Find the area of a triangular garden with sides 30 ft, 40 ft, and 50 ft.

Frequently Asked Questions

What is Heron's formula?
Heron's formula calculates the area of a triangle when you know all three side lengths. It uses the semi-perimeter (s = (a+b+c)/2) and the formula: area = √(s(s-a)(s-b)(s-c)). This calculator applies that formula automatically.
Can I use this calculator for any triangle?
Yes, as long as the three side lengths satisfy the triangle inequality: the sum of any two sides must be greater than the third. If not, the triangle is impossible, and the calculator will indicate an error.
What units does the calculator use?
The calculator accepts side lengths in any consistent unit (e.g., meters, feet, inches). The area result will be in square units of the same unit (e.g., square meters, square feet).

Tips & Common Mistakes

Tips

  • Ensure all side lengths are in the same unit before entering them.
  • Double-check that the side lengths satisfy the triangle inequality (a+b > c, a+c > b, b+c > a).
  • For very large or very small numbers, use scientific notation if needed, but keep units consistent.
  • Use the result as an estimate; for precise engineering or legal purposes, consult a professional.

Common Mistakes to Avoid

  • Entering side lengths in different units (e.g., meters and feet) without converting, leading to incorrect area.
  • Forgetting to check the triangle inequality, which can result in an error or nonsensical area.
  • Misreading the output: the area is in square units, not linear units.

Last updated: August 13, 2026