Mathematics · Geometry

Pythagorean Theorem Calculator

Find the hypotenuse of a right triangle from its two legs.

Runs locally
Your numbers

Inputs and results stay in this browser. Change one value at a time to explore the relationship.

Live constructionRight triangle
Right triangleA triangle labelled with the current entered dimensions.b = 4a = 3c = 5

Change an input to reshape this diagram.

Your inputCalculatedPassed forward in chains
Hypotenuse c5

Calculation steps

  1. Square the legs: 3² = 9; 4² = 16.
  2. Add: 9 + 16 = 25.
  3. Take the square root: c = 5.

Understand Pythagorean theorem

One idea, three depths

Choose how deeply to explain Pythagorean theorem

Pythagorean theorem: Find the hypotenuse of a right triangle from its two legs.

Age 5Explain it to a 5-year-oldStart with a picture

Imagine using Pythagorean theorem to answer this question: find the hypotenuse of a right triangle from its two legs? Enter Leg a and Leg b; the calculator shows Hypotenuse c. For example: Legs 3 and 4 produce hypotenuse √(9 + 16) = 5. The answer tells you Hypotenuse c.

Age 15Explain it to a 15-year-oldConnect it to the formula

For a right triangle, the square of the hypotenuse equals the sum of the squares of the legs. The rule is c = √(a² + b²). Its input values are Leg a, Leg b, and the main result is Hypotenuse c. For example: Legs 3 and 4 produce hypotenuse √(9 + 16) = 5.

CollegeExplain it at college levelState the model precisely

This calculator evaluates the stated pythagorean theorem relation over the valid real-number domain stated below. The implemented relation is c = √(a² + b²), evaluated from Leg a, Leg b to produce Hypotenuse c. For a right triangle, the square of the hypotenuse equals the sum of the squares of the legs. This relationship applies only to right triangles, and c is always the hypotenuse.

Inputs and valid domain

  • Leg a must be a finite real number, at least 0.
  • Leg b must be a finite real number, at least 0.

Important boundary: This relationship applies only to right triangles, and c is always the hypotenuse.

The formula

c = √(a² + b²)

How the calculator works through it

It substitutes Leg a, Leg b into the formula and exposes every numerical step above. The main output is Hypotenuse c.

Read the result correctly

The Hypotenuse c is the direct answer to “find the hypotenuse of a right triangle from its two legs.” Read it with the units shown beside the inputs; a sign, angle, percentage or rate changes what the number means.

A worked check

Legs 3 and 4 produce hypotenuse √(9 + 16) = 5.

Where this model stops being reliable

This relationship applies only to right triangles, and c is always the hypotenuse.

Learn it by changing one value

Begin with the worked example, then change one value while keeping the others fixed. Compare the new result and calculation steps to identify which part of the formula changed.

Dictionary terms behind this calculator

Before studying the codeWhat you should know firstUse the calculator immediately, or check the foundations before reading the implementation.

These foundations help you understand why Pythagorean theorem works. They never block the calculator, and “optional” means useful context rather than a hidden requirement.

Hard requirements

  • Reading formulas and substituting values

    Pythagorean theorem uses c = √(a² + b²). You need to recognise what each side represents before substituting the stated inputs or rearranging the relationship.

    Review this foundation about 4 min

Strong support

Optional enrichment

  • Angles and geometric relationships

    Angle language provides useful geometric context for extending Pythagorean theorem to related shapes and constructions.

    Review this foundation about 4 min
Learn the missing foundationsI already know these — show the code

Mathematics → algorithm → program

Implement this calculation in code

These are direct reference implementations of the calculator's principal relationship and first output. They run locally and include a small known-answer check where the language supports it.

Algorithm

  1. Read Leg a, Leg b.
  2. Evaluate the principal relationship: c = √(a² + b²).
  3. Return Hypotenuse c and check the domain conditions described above.
Python
            from math import *

def pythagorean_theorem(a, b) -> float:
    return sqrt(((a * a) + (b * b)))

assert abs(pythagorean_theorem(3, 4) - 5) < 1e-6 * max(1.0, abs(5))
          
Current calculator valuesUpdates when you change an input above.
              
            
C
            #include <assert.h>
#include <math.h>

double pythagorean_theorem(double a, double b) {
    return sqrt(((a * a) + (b * b)));
}

int main(void) {
    const double expected = 5;
    const double actual = pythagorean_theorem(3, 4);
    assert(fabs(actual - expected) < 1e-6 * fmax(1.0, fabs(expected)));
}
          
Current calculator valuesUpdates when you change an input above.
              
            
C++
            #include <cassert>
#include <cmath>
#include <numbers>

double pythagorean_theorem(double a, double b) {
    return std::sqrt(((a * a) + (b * b)));
}

int main() {
    constexpr double expected = 5;
    const double actual = pythagorean_theorem(3, 4);
    assert(std::fabs(actual - expected) < 1e-6 * std::fmax(1.0, std::fabs(expected)));
}
          
Current calculator valuesUpdates when you change an input above.
              
            
Linux x86-64 assembly

x86-64 NASM · System V ABI · Linux · SSE2 with libm where required

            ; double pythagorean_theorem(double a, double b)
; Linux x86-64 NASM · System V ABI · first eight doubles in xmm0–xmm7
global pythagorean_theorem
section .text

pythagorean_theorem:
    push rbp
    mov rbp, rsp
    sub rsp, 48
    movsd [rbp-8], xmm0
    movsd [rbp-16], xmm1
    movsd xmm0, [rbp-8]
    mulsd xmm0, [rbp-8]
    movsd [rbp-40], xmm0
    movsd xmm0, [rbp-16]
    mulsd xmm0, [rbp-16]
    movsd [rbp-48], xmm0
    movsd xmm0, [rbp-40]
    addsd xmm0, [rbp-48]
    movsd [rbp-32], xmm0
    sqrtsd xmm0, [rbp-32]
    movsd [rbp-24], xmm0
    movsd xmm0, [rbp-24]
    leave
    ret
          
Current calculator valuesUpdates when you change an input above.
              
            
MATLAB
            function result = pythagorean_theorem(a, b)
    result = sqrt(((a * a) + (b * b)));
end
          
Current calculator valuesUpdates when you change an input above.
              
            
Wolfram Language
            ClearAll[mwCalculate];
mwCalculate[a_, b_] := Sqrt[((a * a) + (b * b))];
          
Current calculator valuesUpdates when you change an input above.
              
            

Continue in mathematical software

The downloaded file includes your current inputs and first calculated result. It is created locally.

Floating-point answers can differ slightly by language, compiler and processor. Compare within a suitable tolerance rather than assuming every decimal representation will be identical.

Supporting sourcesAcademic referencesPrimary standards, textbooks and complete citations

Standards, reading and academic references

Use the calculator as the worked interaction, then consult the primary standards and academic textbooks listed below. MW SysArc links to the original sources; the explanation on this page is original and does not reproduce them.

Algebra and Trigonometry 2e

Read the related free OpenStax mathematics chapters
Cite this book
APA 7
Abramson, J. (2021). Algebra and trigonometry 2e. OpenStax. https://openstax.org/books/algebra-and-trigonometry-2e/pages/1-introduction-to-prerequisites
MLA 9
Abramson, Jay. Algebra and Trigonometry 2e. OpenStax, 2021, https://openstax.org/books/algebra-and-trigonometry-2e/pages/1-introduction-to-prerequisites.
Chicago author-date
Abramson, Jay. 2021. Algebra and Trigonometry 2e. Houston, TX: OpenStax. https://openstax.org/books/algebra-and-trigonometry-2e/pages/1-introduction-to-prerequisites.

OpenStax entries are free to read online. Follow the licence shown on each linked source before redistributing or adapting its content.

Reuse the page responsiblyCite this pageAPA, MLA, Chicago, Harvard, BibTeX and RIS

These formats cite this calculator page itself. They are separate from the academic references above, which support the mathematical method and terminology.

APA 7

MW SysArc. (2026, July 21). Pythagorean Theorem Calculator. MW SysArc Tools. https://math.mwsysarc.com/geometry/pythagorean-theorem-calculator

MLA 9

MW SysArc. “Pythagorean Theorem Calculator.” MW SysArc Tools, 21 July 2026, https://math.mwsysarc.com/geometry/pythagorean-theorem-calculator. Accessed 30 Aug. 2026.

Chicago 17

MW SysArc. “Pythagorean Theorem Calculator.” MW SysArc Tools. Published July 21, 2026. Accessed August 30, 2026. https://math.mwsysarc.com/geometry/pythagorean-theorem-calculator.

Harvard

MW SysArc (2026) ‘Pythagorean Theorem Calculator’, MW SysArc Tools. Published 21 July 2026. Available at: https://math.mwsysarc.com/geometry/pythagorean-theorem-calculator (Accessed: 30 August 2026).

BibTeX and RIS records

BibTeX

@misc{mwsysarc_pythagorean_theorem_2026,
  author = {{MW SysArc}},
  title = {Pythagorean Theorem Calculator},
  howpublished = {MW SysArc Tools},
  year = {2026},
  url = {https://math.mwsysarc.com/geometry/pythagorean-theorem-calculator},
  note = {Published July 21, 2026; accessed August 30, 2026}
}

RIS

TY  - ELEC
AU  - MW SysArc
TI  - Pythagorean Theorem Calculator
T2  - MW SysArc Tools
PY  - 2026
DA  - 2026-07-21
Y2  - 2026-08-30
UR  - https://math.mwsysarc.com/geometry/pythagorean-theorem-calculator
N1  - Published July 21, 2026
ER  -

Clear answers

Frequently asked questions

What does the Pythagorean theorem do?

Find the hypotenuse of a right triangle from its two legs.

How does the Pythagorean theorem work?

The calculator applies c = √(a² + b²). For a right triangle, the square of the hypotenuse equals the sum of the squares of the legs.

What can I learn from the Pythagorean theorem?

It connects the mathematical rule to your chosen numbers and shows each calculation step. Change one input at a time to see how the result responds.

Does MW SysArc receive or store what I enter?

No. The calculation runs locally in your browser. MW SysArc does not receive or store your calculation inputs.

How should I use the result?

Use the steps to understand the method, then verify important school or professional work using the notation and rounding rules required in your setting.

Last reviewed . Calculations tested .

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