Master triangle fundamentals: definitions, classification by sides and angles, the angle sum theorem, triangle inequalities, and multiple area formulas—all in one comprehensive lesson.
Calculate the area of any triangle using base and height measurements. Learn the fundamental triangle area formula with step-by-step calculations and visual examples.
The length of the triangle's base (any side can be the base)
The perpendicular distance from the base to the opposite vertex
Enter the base and height measurements, then click "Calculate Area" to find the triangle's area.
The triangle area formula Area = ½ × base × height is fundamental in geometry. It works because a triangle is exactly half of a parallelogram with the same base and height.
Base
Any side of the triangle can serve as the base. It doesn't have to be the bottom side!
Height
The perpendicular distance from the base to the opposite vertex. Always forms a 90° angle with the base.
Why ÷ 2?
A triangle is exactly half the area of a rectangle with the same base and height dimensions.
Construction & Architecture
Calculating roof areas, triangular garden plots, and structural supports
Art & Design
Creating triangular patterns, logos, and calculating material needed for triangular shapes
Navigation & Surveying
Measuring land areas, calculating distances, and triangulation in GPS systems
Rectangle Area = base × height
Triangle Area = (base × height) ÷ 2
A triangle has exactly half the area of a rectangle with the same base and height
Explore different methods of calculating triangle area and related concepts.
Try other triangle calculators and geometry tools.
A triangle is a polygon with exactly three vertices, three sides, and three interior angles. It is the simplest closed figure you can create with straight lines.
Side is opposite vertex A (connecting vertices B and C). This naming convention is used throughout geometry and trigonometry.
If you fix the lengths of all three sides, the triangle's shape is completely determined. Unlike quadrilaterals (which can flex), triangles cannot deform without breaking a side. This is why triangles appear everywhere in construction: roof trusses, bridges, bicycle frames.