Triangle Area Calculator
Calculate the area of a triangle from a positive base and its corresponding perpendicular height in consistent units.
Calculate triangle area
How this tool works
Triangle area depends on a selected base and the height measured perpendicular to that base. The calculator intentionally labels perpendicular height because using a sloping side length would produce an incorrect result.
Area equals one half multiplied by base multiplied by perpendicular height. Base and height must use the same length unit for the result to be in square units.
How to use it
- Choose one side as the base and enter its positive length.
- Enter the perpendicular distance from that base to the opposite vertex.
- Read the resulting area in square units.
Worked examples
Integer dimensions
- Input
- Base 12, perpendicular height 7
- Output
- Area 42 square units
Multiplying base and height gives 84, and taking one half produces an area of 42 square units.
Decimal dimensions
- Input
- Base 5.5, perpendicular height 4
- Output
- Area 11 square units
The base-height product is 22. Dividing by two gives eleven, with squared units matching the original measurement system.
Limitations
- A side length is not a valid height unless it is perpendicular to the chosen base.
- This version does not calculate area from three sides or coordinates.