Pythagorean Theorem Calculator
Enter any two positive sides of a right triangle to find the third. The tool uses c² = a² + b² where c is the hypotenuse (longest side). Works whether you measure in inches, feet, centimetres, or metres — keep units consistent in your own working.
One leg next to the right angle. Leave empty if this is what you want to find.
The other leg. Leave empty if this is what you want to find.
Longest side, opposite the right angle. Leave empty if you want to find it from two legs.
Enter any two positive sides of a right triangle to find the third. The tool uses c² = a² + b² where c is the hypotenuse (longest side). Works whether you measure in inches, feet, centimetres, or metres — keep units consistent in your own working.
For legs a and b and hypotenuse c: c² = a² + b² If both legs are known: c = √(a² + b²) If the hypotenuse c and one leg are known: other leg = √(c² − known_leg²)
If a = 3 and b = 4, then c = √(9 + 16) = √25 = 5. If instead c = 13 and a = 5, the other leg is √(169 − 25) = √144 = 12.
It is the side opposite the right angle and is always the longest side. If you label the two shorter sides as legs, the hypotenuse is the remaining side.
Not inside one run of the formula — convert so every side uses the same unit first. The calculator only does the Pythagorean relationship on the numbers you enter.
This tool only applies to right triangles (90° corners). For other triangles you would use different rules such as trigonometry or the cosine rule.
Yes, if the situation forms a right triangle (for example vertical height and horizontal distance along the ground). Model the two perpendicular distances as legs and interpret the result as the sloping length.
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