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Quick guide

What This Calculator Does

This Pythagorean theorem calculator focuses on right-triangle side relationships. It finds hypotenuse c from legs a and b, finds one leg from the hypotenuse and the other leg, or checks whether three entered sides satisfy a² + b² = c².

It answers “what is the missing side?” or “does this side set fit a right triangle?” It is not a full triangle solver: it does not calculate angles, area, perimeter, map distance, or unit conversions.

When to Use It

  • You know both perpendicular legs and want the diagonal or hypotenuse.
  • You know the hypotenuse and one leg and need the other leg.
  • You want to sanity-check a classic Pythagorean triple or a layout measurement.
  • You need a quick mathematical screen for whether three measured lengths are consistent with a right angle.

For non-right triangles or problems that also need angles, area, or perimeter, use the triangle calculator.

Inputs Explained

Calculation mode

The page has four modes: Find Hypotenuse c, Find Leg a, Find Leg b, and Verify Right Triangle. The field that is being solved for becomes read-only; verify mode requires all three sides.

Legs a and b

Read the full guide

Frequently Asked Questions

Which modes does this tool support?

It can find hypotenuse c, find leg a, find leg b, or verify whether three sides satisfy the Pythagorean relationship.

What should I enter to find the hypotenuse?

In Find Hypotenuse c mode, enter the two perpendicular legs a and b; c is returned as the result.

Why must c be larger when finding a leg?

c is the hypotenuse and must be the longest side of a right triangle; otherwise the square root does not produce a valid positive leg.

What is the squared-relation difference?

It is `|a²+b²-c²|`. The page says yes when the difference is below `0.000001`; this is a numeric tolerance, not a field-measurement tolerance standard.

Do the input units need to match?

Yes. The page does not convert centimeters, meters, or inches, so all three sides must use the same unit system.

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Pythagorean Theorem Calculator

Find a hypotenuse from two legs, solve a missing leg, or verify three side lengths with the Pythagorean relationship.

Common Right-Triangle Scenarios

Pick a preset to update the result instantly.

Results

Please enter lengths of sides a and b