Triangle Area Calculator
Whether you have the base and height of the triangle, three sides, side-angle-side, or angle-side-angle, this versatile triangle area calculator will find the area of a triangle for you.
Area30½ × 10 × 6
Base10
Height6
Area of the enclosing rectangle60the triangle is always exactly half
The formula
A = ½ × base × height
The height must be perpendicular
The height is the straight-line distance from the base to the opposite vertex, measured at right angles to the base — not the length of a slanted side. For an obtuse triangle that perpendicular can fall outside the triangle entirely, and the formula still holds.
What always holds
- The three angles add to 180°, without exception.
- Any two sides must add to more than the third — the triangle inequality. Sides of 4, 5 and 12 cannot close.
- The longest side always faces the largest angle.
Area = ½ × base × heightfor any triangle, with the height measured perpendicular to that base.
Which formula to reach for
With three sides, use Heron’s formula. With a base and its height, use ½bh. With two sides and the angle between them, use ½ab·sin C. With a right angle, the two legs are already base and height, so the area is just half their product.