Right Triangle Calculator

A right triangle has one 90° angle, which makes it uniquely solvable — knowing just two pieces of information about it (two sides, or one side and one angle) is enough to work out everything else: the remaining side, both remaining angles, and the area. That predictability is exactly why right triangles anchor so much of trigonometry.

Geometry and trig students use this to solve for whatever's missing given two known values, but the same triangle shows up constantly in construction and design: framing a roof, checking that a ladder is at a safe angle against a wall, calculating a wheelchair ramp's rise and run, or laying out a diagonal brace.

Because a right triangle's shape is fully locked in by any two known measurements, this calculator adapts to whichever two you actually have — two legs, a leg and the hypotenuse, or a leg and an angle — rather than forcing one fixed input layout.

When both legs are known, the Pythagorean theorem finds the hypotenuse directly: a² + b² = c². When the hypotenuse and one leg are known, the same equation is rearranged to solve for the missing leg instead.

When one leg and one angle are known, trigonometric ratios take over: sine, cosine and tangent relate an angle to a ratio of two of the triangle's sides. Once one side and one non-right angle are known, those ratios pin down every other side.

In every case, once all three sides are known, the two non-right angles follow from inverse trig functions, and since a triangle's angles always sum to 180°, the two acute angles in a right triangle always add up to exactly 90°.