Triangle Area Calculator

Enter the base and perpendicular height to get the triangle area.

Base

Perpendicular height

Area = 30bh / 2

Base-height vs Heron triangle validation

Choose the data you actually have. Base + perpendicular height gives area without inventing side lengths; three sides use Heron’s formula and first enforce the triangle inequality, exposing perimeter and semiperimeter only when that geometry is valid.

Known measurementsBasePerpendicular heightSide aSide bSide cLinear unit

—Area

—Perimeter

—Semiperimeter

—Geometry status

Ready.

Check	Value	Rule	Meaning

Base-height mode does not fabricate a perimeter. Heron mode requires three positive sides satisfying a+b>c, a+c>b and b+c>a.

Use consistent measurements and valid geometric assumptions

Keep linear inputs in a consistent unit, verify that side lengths or coordinate points can form the stated shape, and treat sketches as explanatory unless explicitly marked to scale. Coordinate formulas can become unstable for nearly degenerate shapes, so invalid or nearly collinear inputs are rejected rather than silently returning misleading values.