Triangle Area Calculator
Calculate triangle area from base and height or from three side lengths using Heron's formula, free in your browser.
Enter Values
Shape
How to use this calculator
- Enter the base and the perpendicular height.
- Press Calculate for the area.
How it works
The area of a triangle is ½ × base × height, where the height is measured at a right angle to the base.
Worked example
Base 6 m, height 4 m. Area = ½ × 6 × 4 = 12 m².
Common mistakes
- Using a slanted side as the height — the height must be perpendicular to the base.
- Forgetting the ½ — base × height alone gives a rectangle, double the triangle.
Frequently asked questions
Which height do I use?
The perpendicular height — measured at a right angle from the base to the opposite point — not the length of a slanted side.
Does this work for any triangle?
Yes. ½ × base × height works for every triangle, as long as the height is taken at a right angle to the base you entered.
Related tools
- Rectangle Area Calculator
- Trapezoid Area Calculator
- Pythagorean Theorem Calculator
- Circle Area Calculator
- Cube Volume Calculator
- Cylinder Volume Calculator
Explore more in Geometry, Shape, Area & Volume.
Cite this tool
Zerdly. (2026). Triangle Area Calculator. Retrieved from https://www.zerdly.com/tools/triangle-area-calculator/
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.