Calculate the hypotenuse or a leg of a right triangle using the Pythagorean theorem. Fill in two of the three sides and leave the third at 0, and the calculator works out the rest.
In a right triangle, a and b are the two legs (the sides that meet at the right angle), while c is the hypotenuse — the side opposite the right angle. The hypotenuse is always the longest side in a right triangle.
If you know two of the sides, you can solve the equation for the third: c = √(a² + b²) to find the hypotenuse, or a = √(c² − b²) to find a leg.
The Pythagorean theorem is used to find distances, check whether a corner is 90 degrees (for example in construction and carpentry), and calculate diagonals in rectangles and other practical measurements.
No, the Pythagorean theorem only applies to right triangles — triangles with one corner at exactly 90 degrees. For other triangles you need other methods, such as the law of cosines.
Then the calculator uses the numbers to check whether they actually satisfy the Pythagorean theorem, i.e. whether a² + b² actually equals c². This is useful if you want to verify whether a triangle is a right triangle.