How to use this calculator
Choose one side as the base. Measure the perpendicular distance from the opposite vertex to the line through that base. The height can fall outside an obtuse triangle.
Formula
A = b × h ÷ 2
Worked example
A triangle with base 10 m and perpendicular height 6 m has area 10 × 6 ÷ 2 = 30 m².
Assumptions and limits
Base and height determine area but not all side lengths. Perimeter is not calculated because these inputs do not uniquely determine it.
Frequently asked questions
Can the height be outside the triangle?
Yes. In an obtuse triangle the perpendicular height may meet an extension of the base.
What units should I use?
Choose your input unit, then enter every dimension in that unit. The result unit can be changed independently.
Does this include waste or material costs?
No. This is geometric area only. Add openings, overlap, cutting waste, prices and installation requirements separately.
Calculated locally; rounded only for display.