Triangle Area Calculator (3 sides, Heron’s formula)
Find a triangle’s area from its three sides with Heron’s formula. For triangular land pieces and for study.
Quick answer
Sides 30, 40, 50: area 600 sq units.
How it is calculated
- Half perimeter s = (a + b + c) ÷ 2 = 60.
- Area = √(s × (s−a) × (s−b) × (s−c)) = √(60 × 30 × 20 × 10).
- = √3,60,000 = 600.
Worked example
Sides are 30, 40 and 50. Half perimeter 60, area 600 sq units. (It is a right triangle: ½ × 30 × 40 = 600.)
| Side A | 30 |
| Side B | 40 |
| Side C | 50 |
| Area | 600 sq units |
Formula
Area = heron(a,b,c)
Good to know
- The longest side must be shorter than the other two added, or there is no triangle.
- The area comes in square units of whatever unit you enter.
Questions people ask
What is Heron’s formula?
Area = √(s(s−a)(s−b)(s−c)), with s = (a+b+c)/2.
What if I know the height?
Area = ½ × base × height.
Sides in feet?
The result is in sq ft; divide by 9 for sq yards.
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Updated 13 Nov 2026 · Desktop N Calculator v1.2.0