GCF and LCM Calculator

This calculator works out the greatest common factor (GCF) and the lowest common multiple (LCM) of two or more whole numbers in one step, saving you long division or trial and error when you need both figures for schoolwork, everyday maths or programming. Type your numbers into the single input field, separated by commas or spaces, and the calculator recalculates instantly as you type. It returns the greatest common factor, the largest whole number that divides every number you entered with nothing left over, and the lowest common multiple, the smallest whole number that every one of your numbers divides into exactly. Behind the scenes it applies the Euclidean algorithm to find the GCF efficiently, then uses the relationship between GCF and LCM to work out the second figure without a lengthy search through multiples. Because it works with any number of values, not just pairs, you can check three, four or more numbers at once, handy when adding several fractions with different denominators or simplifying a ratio to its lowest terms. Use the GCF to reduce a fraction or ratio to its simplest form, and the LCM to find a common denominator when adding or comparing fractions. Below the calculator, a worked example and a short explanation of the method walk through exactly how each result is reached.

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