Geometry & Shapes
Pythagorean Theorem Calculator
Pythagorean Theorem: it applies the Pythagorean theorem a² + b² = c² to find the missing side of a right triangle. Worked through below with real figures, and the calculator repeats the working on your own inputs — free, on-device, instant.
Want to find a missing side of a right triangle? Pythagorean Theorem Calculator does it from any two of side a, side b and side c (leave the unknown blank) and shows the missing side length clearly, with everything calculated in your browser.
About this calculator
It matters whenever a shape has to be measured, cut, covered or compared and the geometry has to be right first. The governing relationship: It applies the Pythagorean theorem a² + b² = c² to find the missing side of a right triangle. See it on real numbers: With legs a=6 and b=8: c = √(6² + 8²) = √(36+64) = √100 = 10 . The calculator above applies the same steps to whatever you enter — computed locally, nothing sent anywhere.
How to use
- Enter the two sides you know (a, b, or c).
- Leave the unknown side blank.
- Press Calculate to find the missing side.
- Read the missing side, found from the Pythagorean theorem.
Why use Pythagorean Theorem Calculator
Fast
Calculations run in your browser. No round trip to a server.
Private
Your inputs never leave your device. Nothing is uploaded.
Free
No signup, no paywall, no ads-in-results, no watermarks.
Accurate
Uses standard formulas where applicable; check critical results before relying on them.
Mobile-ready
Optimised for phones, tablets, and desktops alike.
Transparent
Honest disclaimers wherever browser limits or regional rules apply.
Common uses
Use it when laying out a square corner on site
Use it for a diagonal across a rectangle
Use it when sizing a ramp or staircase run
Use it for a quick right-triangle check
Use it for the hypotenuse from two legs
Pythagorean Theorem in construction and carpentry layout
Technical notes
Pythagorean Theorem Calculator applies the Pythagorean theorem a² + b² = c² to find the missing side of a right triangle.
Side lengths are taken exactly as entered and the result assumes a right triangle; it does not check real-world measurement error beyond the triangle rule.
All arithmetic runs in your browser using double-precision floating point, so extreme inputs may show tiny rounding differences.
FAQ
Can I solve for a leg, not just the hypotenuse?
Yes. Enter any two of the three sides and leave the unknown blank, and the calculator solves for it.
Which side is the hypotenuse?
Side c is the hypotenuse, the longest side opposite the right angle; it must be larger than either leg.
What if I enter all three sides?
The calculator asks you to leave exactly one side blank, since it solves for a single missing value.
Does the Pythagorean Theorem Calculator send my data to a server?
No. The Pythagorean Theorem Calculator runs entirely in your browser, so nothing you enter is uploaded, stored, or shared.
Worked example
With legs a=6 and b=8: c = √(6² + 8²) = √(36+64) = √100 = 10.