What is the least common denominator?

The LCD is the smallest number that all denominators divide into—i.e. the LCM of the denominators.

Why do I need the LCD?

To add or subtract fractions, you must express them with the same denominator; the LCD keeps the numbers as small as possible.

For a set of fractions, LCD = LCM(denominator1, denominator2, …).

Find the least common denominator (LCD) of two or more fractions. LCD is the LCM of the denominators.

Denominators (comma or space separated, e.g. 2, 3, 4)

Result

LCD = 12

What is the least common denominator?: The LCD is the smallest number that all denominators divide into—i.e. the LCM of the denominators.
Why do I need the LCD?: To add or subtract fractions, you must express them with the same denominator; the LCD keeps the numbers as small as possible.
How is LCD related to LCM?: For a set of fractions, LCD = LCM(denominator1, denominator2, …).

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