Frequently Asked Questions
Everything you need to know about the Pythagorean Theorem Calculator.
What is the Pythagorean theorem?
The Pythagorean theorem states that in a right triangle, the square of the hypotenuse (c) equals the sum of the squares of the two legs (a and b): a² + b² = c².
Which side is the hypotenuse?
The hypotenuse is always the longest side of a right triangle, located opposite the 90° angle.
Can I solve for a leg instead of the hypotenuse?
Yes. Enter one leg and the hypotenuse, and the calculator solves for the missing leg using b = √(c² − a²).
Does this only work for right triangles?
Yes, the Pythagorean theorem only applies to right triangles — triangles with exactly one 90° angle.
Why does the hypotenuse have to be longer than each leg?
Because the hypotenuse is the longest side of a right triangle by definition; if a given 'hypotenuse' value were shorter than a leg, no valid right triangle exists.
Can I use decimal or fractional side lengths?
Yes, the calculator accepts any positive decimal value for the side lengths.
What real-world problems use the Pythagorean theorem?
Common uses include finding a ladder's required length, a TV or monitor's diagonal size, the diagonal of a rectangular room, and distances in navigation or construction.
Does the calculator show the triangle's area?
Yes, once both legs are known, the area (½ × a × b) is shown alongside the side lengths.
How many sides do I need to enter?
Enter exactly two of the three sides; the calculator solves for the third automatically.
Is this calculator free to use?
Yes, the Pythagorean theorem calculator is completely free with no sign-up, and all calculations run instantly in your browser.