Overview
The area of a triangle is half the product of its base and height. The formula works for every triangle as long as the height is perpendicular to the base. Choosing any side as the base gives the same area when the matching height is used.
Formula
Area = ½ × base × height.
How it works
Choose the base
Pick one side of the triangle as the base.
Find the height
Measure the perpendicular distance from the opposite vertex to the base.
Multiply and halve
Multiply the base by the height, then divide by 2.
Read the result
The area is expressed in square units.
Worked examples
Example 1: base 12 and height 8
Area = (12 × 8) ÷ 2 = 48 square units.
Example 2: base 7 and height 4.5
Area = (7 × 4.5) ÷ 2 = 15.75 square units.
Frequently asked questions
Does the triangle need to be right-angled?
No. The formula works for all triangles as long as the perpendicular height is used.
What if the height falls outside the triangle?
That can happen in an obtuse triangle, but the area remains correct using the absolute height.
How do I find the area from three sides?
Use Heron's formula, which uses the semiperimeter and the three side lengths.
This calculator is for educational and informational purposes only and is not a substitute for professional advice.