Pythagorean Theorem Calculator
Use this Pythagorean theorem calculator to find a missing side of a right triangle. Enter any two side lengths and the calculator will solve the third side using a² + b² = c².
How to Use the Pythagorean Theorem Calculator
Enter any two positive side lengths of a right triangle and leave the unknown side blank. The calculator uses a² + b² = c² to solve the missing side.
Practical Example
If the legs are 3 and 4, the hypotenuse is √(3² + 4²) = 5.
Factors That Affect the Result
The theorem applies only to right triangles. The hypotenuse must be the longest side, and all lengths should use the same unit.
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Frequently Asked Questions
Does this work for every triangle?
No. The Pythagorean theorem is for right triangles.
Which side is c?
c is the hypotenuse, opposite the 90-degree angle.
Can the result be a decimal?
Yes. Many right triangles have irrational side lengths.
Applying the Pythagorean Theorem
The Pythagorean theorem applies to right triangles and states that a² + b² = c², where c is the hypotenuse opposite the right angle. If the two legs are 3 and 4, the hypotenuse is √(3² + 4²) = 5. If the hypotenuse and one leg are known, the other leg can be found by rearranging the formula, such as a = √(c² − b²). All side lengths should use the same unit. The theorem does not directly solve a general non-right triangle; other methods such as the law of cosines may be needed in that case. When entering measured values, the result can only be as accurate as the measurements provided, so avoid excessive decimal precision when the input dimensions are approximate.