Right Triangle Calculator

This calculator finds missing sides and angles of a right triangle for students, builders, and anyone checking a diagonal.

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Enter two known sides, or one side and one acute angle. Identify the hypotenuse correctly: it is the longest side and sits opposite the 90-degree angle.

For legs a and b and hypotenuse c, the side formula is c^2 = a^2 + b^2. For angle A, sin(A) = opposite / hypotenuse, cos(A) = adjacent / hypotenuse, and tan(A) = opposite / adjacent.

Worked example

A right triangle with legs of 6 m and 8 m has a hypotenuse of square root of (6^2 + 8^2) = 10 m. The angle opposite the 6 m side is arcsin(6 / 10) = 36.87 degrees, and the other acute angle is 53.13 degrees.

Common questions

Do I need two measurements?

Yes. Besides the known 90-degree angle, you need at least two measurements, including at least one side.

Why do the two acute angles add to 90 degrees?

Every triangle's angles total 180 degrees. Since a right triangle already contains a 90-degree angle, the other two must total 90 degrees.

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