How it works
What this calculadora actually does
Use this Hypotenuse Calculator when you need a hypotenuse calculator you can trust — clean inputs, transparent steps, zero fluff.
If you keep running the same hypotenuse calculator into a text message and squinting at the answer, park it on this page — share the URL instead, the maths travels with it.
This is the kind of problem where a stray decimal costs you the mark. Think of one worked example you can reuse — then crunch the numbers and the rest of this page explains what the answer means.
Square each leg, add them, and take the square root. For legs 3 and 4: √(9 + 16) = √25 = 5.
On this page you will see BBC Bitesize, MathsIsFun and Mathematics treated as first-class terms — each one is linked to the calculators and references that use it, so you can follow the thread without retyping queries into a search bar.
The formula we run is c = √(a² + b²). You'll see each term laid out in the worked example below.
If it helps, jump straight to the Maths hub or compare with the Pythagoras Theorem Calculator and the Triangle Area Calculator — those two calcs are the ones readers usually open right after this page.
Following the method end to end
Here's what happens when you plug real numbers in.
Square each leg, add them, and take the square root. For legs 3 and 4: √(9 + 16) = √25 = 5.
Every run comes back to c = √(a² + b²) — change the inputs, the structure of the answer stays.
Scenarios where Hypotenuse Calculator pays off
Hypotenuse Calculator is aimed at people arriving with questions like these:
- "What is hypotenuse"
- "Hypotenuse formula"
- "Find hypotenuse from legs"
- "What is hypotenuse calculator"
- "How to calculate hypotenuse calculator"
- "Hypotenuse calculator formula"
When it isn't the right tool
Every tool has an edge where it stops being the right answer. Hypotenuse Calculator is no exception:
- For legally binding tax or medical decisions — cross-check with HMRC, NHS or a qualified professional.
- For very large or very small extremes the rounding error outgrows the useful precision.
- When the underlying rate or threshold has changed since the page was last reviewed — always verify with the primary source.
- When the input you have is already a derived figure (net of something) — feeding it in as "gross" will double-subtract.
The snags that cost people the answer
Every time you crunch the numbers for a new scenario, one of these creeps in — it's worth knowing them ahead of time.
- Flipping the numerator and denominator — half the "wrong" answers on this type of calculation are an inverted ratio.
- Not noticing that one input is already pre-rounded by the source that gave it to you.
- Forgetting that negative inputs behave differently — the formula assumes positive magnitudes unless the tool says otherwise.
- Running the calculation once and believing it. Always sanity-check against an order-of-magnitude estimate done in your head.
- Copying numbers from a PDF and picking up hidden thousands separators as decimal points.
The sources behind the numbers
Where the maths needs an external authority, we cross-check against:
- BBC Bitesize
- MathsIsFun
Works well alongside
If this question keeps coming up for you, the same cluster of tools usually comes next:
- Pythagoras Theorem Calculator — Find the hypotenuse or a missing side of a right-angled triangle using a² + b² = c².
- Triangle Area Calculator — Find the area of a triangle using base × height ÷ 2 or Heron's formula.
How we keep this accurate
Our calculadoras run on pure, unit-tested functions — the same logic lives in the browser and in the CI test suite. When tax rates, thresholds or official figures move, the update lands within 24 hours of the announcement. You can read the editorial policy and corrections policy.
Found an out-of-date number on Hypotenuse Calculator or anywhere else in the Maths toolkit? Send it to the editorial desk and we'll patch it. Or browse the full calculadora directory for the next tool you need.