Does the height have to be inside the triangle?
No. It is the perpendicular distance from the base line to the opposite vertex.
Triangle Area Calculator
Calculate triangle area from base and height or from three sides.
Calculations happen locally. We do not send your values to our server.
Example
A triangle with base 10 and height 6 has area 30. With three sides, the calculator can instead apply Heron’s formula.
Calculation method
Base-height mode uses base × height ÷ 2. Three-side mode finds semiperimeter s and uses √(s(s−a)(s−b)(s−c)).
Important notes
All lengths must use the same unit, and three entered sides must satisfy the triangle inequality.
Frequently asked questions
What if I know only three sides?
Select the three-sides method to calculate area with Heron’s formula.
Why are some three-side inputs rejected?
Two side lengths must always add to more than the remaining side.