Triangle Area Calculator (Base x Height)
Calculate the area of any triangle instantly using its base and height. Formula: Area = 1/2 x base x height. Fast, accurate, free.
How to use this tool
- Enter base and height in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your area and the full breakdown beneath it.
Formula
Area = 1/2 x base x height
How it works
Multiply the base by the perpendicular height, then divide by 2. The height must be measured at a right angle to the base.
Worked example
Right triangle with base 6 m and height 4 m
- Area = 1/2 x 6 x 4
- Area = 1/2 x 24
- Area = 12 m^2
12 m^2
Common mistakes to avoid
- Using a slant side length instead of the perpendicular height; the height must be measured at a right angle to the base.
- Forgetting to multiply by 1/2, computing base x height instead of (1/2) x base x height.
- Mixing units between base and height (e.g. base in feet, height in inches) without converting first.
Key terms
- What is the base of a triangle?
- Any side of the triangle chosen as the reference side.
- What is the height (altitude)?
- The perpendicular distance from the base to the opposite vertex.
Frequently asked questions
- How do I find the height if I only know the three sides?
- Use Heron's formula to compute the area from the three sides, then rearrange: height = 2 x Area / base.
- Does this formula work for obtuse triangles?
- Yes. For an obtuse triangle the perpendicular height may fall outside the triangle, but the formula Area = 1/2 x base x height remains valid.
- Can I use any side as the base?
- Yes, as long as you use the corresponding perpendicular height for that side. Each base-height pair gives the same area.