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Triangle Area Calculator
Find triangle area from three side lengths using Heron's formula. Validate the triangle and calculate its perimeter.
- Area
- 6 square units
- Perimeter
- 12
- Semiperimeter
- 6
How the calculation works
Semiperimeter p = (a + b + c)/2. Heron's formula: A = √(p(p − a)(p − b)(p − c)).
Inputs
- Side a
- Side b
- Side c
Calculation details
Each side must be shorter than the sum of the other two. Sides 3, 4, and 5 give area 6 and perimeter 12.
Enter all three lengths in the same unit. Centimeter inputs give square centimeters. A numerically stable rearrangement of Heron's formula is used.
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Updated: 2026-10-02