Pythagorean theorem calculator
Fill in what you know and leave the unknown box empty — it works out whichever one is missing. Nothing is uploaded; the arithmetic happens in your browser.
The formula
a² + b² = c²
Where this usually goes wrong
c is the hypotenuse — the side opposite the right angle, and always the longest. Putting a leg in the c box is the usual mistake.
Worked example
The 3-4-5 triangle: legs of 3 and 4 give a hypotenuse of 5.
Those numbers are already in the boxes above — press Work it out to see it, then change them for your own.
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