Right Triangle Area Calculator
Calculate a right triangle’s area from its two perpendicular legs. Do not enter the sloping hypotenuse as a leg.
How to use Right Triangle Area Calculator
1. Choose Measurement Unit, then enter Leg A, Leg B without a unit suffix. 2. Use the selected ordinary, square or cubic unit for each measurement as explained below; changing the selector relabels inputs and does not convert them. 3. Select Calculate, or press Enter, and read right triangle area. 4. Select Select Copy result to copy the answer, or Reset to clear the form.
Why use this tool?
Find the area of a triangular corner or right-angled drawing when the two sides forming the right angle are known.
How the calculation works
Area = leg A × leg B ÷ 2. The right angle makes either leg the perpendicular height relative to the other. Results use up to six decimal places. Tiny nonzero results below 0.000001 use scientific notation with six significant digits. Browser floating-point arithmetic can introduce small rounding differences. Inputs and calculated magnitudes must not exceed 9,007,199,254,740,991. Negative physical measurements and arithmetic underflow are rejected. Zero dimensions are treated as a degenerate limit where the formula allows them; divisors and sides of an actual triangle must be positive. Formula reference: https://openstax.org/books/prealgebra-2e/pages/c-geometric-formulas
Example
Leg A = 6 cm and Leg B = 8 cm give 6 × 8 ÷ 2 = 24 cm².
Practical tip
Identify the two sides touching the right-angle marker. Their order does not affect the area.
Frequently asked questions
Can I use a leg and the hypotenuse?
Not directly. First find the other leg using the Right Triangle Missing Dimension Calculator, then enter both perpendicular legs here.
What if the triangle is not right-angled?
Use base and perpendicular height in the Triangle Area Calculator. Multiplying two arbitrary sides and dividing by two is not generally correct.
Does changing Measurement Unit convert my numbers?
No. The selector states the unit of the numbers you enter and labels the answer. Convert measurements first when changing units. Area inputs use square units and volume inputs use cubic units; result precision follows the rounding method above.