Heron’s formula
Find a triangle’s area using its three sides.
Inputs
Use the units shown—
Enter your values and select Calculate.
Formula & explanation
s = (a+b+c)/2; A = √[s(s−a)(s−b)(s−c)]
Variables & units
- Side a
- cm · minimum 0, maximum 1000000000
- Side b
- cm · minimum 0, maximum 1000000000
- Side c
- cm · minimum 0, maximum 1000000000
Worked example
Sides 3, 4, 5 cm give s = 6 cm and area = 6 cm².
Assumptions
The sides must form a non-degenerate triangle. Computation uses an equivalent stable form of Heron’s formula.
Formula version 1.0.0. JavaScript floating-point arithmetic applies. Results display up to 6 decimal places; stored values retain available precision. Use the units shown.
Practice with an example
Use the default input values to find the answer. The reset icon restores those values.
Calculated on your device. Your latest 100 calculations stay in this browser.