Euclid’s Algorithm Calculator

  • Enter two numbers to find their greatest common divisor (GCD).
  • Click "Calculate GCD" to compute the GCD using Euclid's Algorithm.
  • The detailed calculation and explanation will be displayed below.
  • Your calculation history will appear below the results.
  • Use "Clear Results" to reset the results and "Copy Results" to copy the GCD to the clipboard.

Find the greatest common divisor (GCD) of two numbers.


Calculation and Explanation:
Calculation History:

    Euclid’s algorithm is an efficient method for finding the greatest common divisor (GCD) of two integers. Also known as the Euclidean algorithm, it is one of the oldest algorithms still in use today and continues to serve as the basis for many GCD calculations in modern applications. This article will provide an in-depth explanation of Euclid’s algorithm, its conceptual formula, key benefits, and some interesting historical facts, all without delving into any programming code.

    How Euclid’s Algorithm Works

    Euclid’s algorithm utilizes the principle that the GCD of two integers does not change if the smaller integer is subtracted from the larger one. By continuously replacing the larger integer with the difference between the smaller and larger integers, the algorithm quickly reduces the numbers to their greatest common diviso.

    Conceptual Formula

    The conceptual formula behind Euclid’s algorithm is: GCD(a, b) = GCD(b, remainder of a/b) Where GCD refers to greatest common divisor, while “a” and “b” are the two given integers. The algorithm uses this recursive formula, subtracting the smaller from the larger number until reaching GCD.

    Steps of Euclid’s Algorithm

    To find the GCD of two integers using Euclid’s algorithm:

    1. Divide the larger integer “a” by the smaller integer “b”
    2. Set the remainder from step 1 as the new value for “a”
    3. Replace value “b” with the last value of “a”
    4. Repeat steps 1-3 until the remainder is 0.
    5. The last non-zero remainder value is the GCD.

    Key Benefits

    Some of the key benefits of Euclid’s algorithm include:


    The logic of Euclid’s GCD algorithm is very straightforward, making it easily understood and implemented. No matter the size of the integers, the process remains the same.


    Rather than tediously checking all possible factors, Euclid’s method narrows in on the GCD rapidly through its recursive remainder process. This efficiency has allowed it to stand the test of time over 2,000 years.

    Builds Intuition

    By computing many examples by hand, Euclid’s algorithm allows one to build an intuition about number theory properties like factorization and primes. Mastery helps cement important abstract mathematical concepts.

    Adaptability in Programming

    The clarity of Euclid’s structure enables it to function as an introductory example when teaching recursive programming for different coding languages.

    Interesting Historical Facts

    First described in Euclid’s Elements (circa 300 BC), this algorithm predated computer programming languages by over 2,000 years!

    Euclid presented this efficient “junior-level” GCD calculation as Proposition VII in Book 2 of his foundational math treatise, which was widely used into the 19th century.

    Euclid likely did not discover the algorithm but presented following his usual methodology of providing rigorous proofs for known mathematical facts.


    In conclusion, Euclid’s algorithm is an elegant, easily understood recursive method for finding the greatest common divisor of two integers with substantial advantages in simplicity, efficiency, conceptual understanding, and adaptability. Its longevity as an algorithm standard for over 23 centuries points to its fundamental soundness and utility across ages. Studying Euclid’s GCD calculation provides insight into the nature of factorization and Euclid’s genius in codifying elemental math processes. Math students today still benefit from learning an algorithm Euclid likely presented not as an invention, but a timeless mathematical truth grounded in logic.


    1. Ball, W. W. R. (2011). A short account of the history of mathematics. Cambridge University Press.
    2. Boyer, C. B., & Merzbach, U. C. (2011). A history of mathematics. John Wiley & Sons.
    3. Calinger, R. (Ed.). (1995). Vita mathematica: Historical research and integration with teaching. MAA.
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