Least Common Denominator (LCD) Calculator

Find the Least Common Denominator (LCD) of the given fractions.

Converted Fractions with the common LCD:
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How to use this calculator?

1. Enter the comma-separated fractions. For example 1/2, 5/4 or 2 2/4, 7/3.

2. Click on the "Calculate" button.

3. Get your LCD.

4. Optionally, check your fractions converted to the LCD.

What is the Least Common Denominator?

The Least Common Denominator is the smallest multiple that two or more numbers have in common. Basically, it's the smallest number that can be evenly divided by all the numbers you're working with.

The LCD is particularly useful when you're dealing with fractions and want to add, subtract, or compare them (check out our fraction calculator!).

Fractions are numbers that represent a part of a whole, like 3/4 or 2/5. The denominator in a fraction is the number at the bottom, which tells you how many equal parts the whole is divided into.

When you have fractions with different denominators, it's challenging to directly compare or combine them. That's when you find the LCD to make the denominators the same. By doing this, you can easily compare and operate on the fractions.


Let's say we have the fractions 1/3 and 2/5. To add or subtract these fractions, we need to find their LCD. The denominators are 3 and 5, so we're looking for the smallest number that both 3 and 5 divide into evenly.

To find the LCD, you can use various methods, like finding the multiples of the numbers or using prime factorization. In this case, the LCD of 3 and 5 is 15. Both 3 and 5 divide evenly into 15.

Now, we rewrite the fractions with the common denominator of 15. For 1/3, we multiply the numerator and denominator by 5 to get 5/15. For 2/5, we multiply the numerator and denominator by 3 to get 6/15.

When both fractions have the same denominator, we can easily add or subtract them. In this example, 5/15 + 6/15 equals 11/15.

More Examples

Numbers LCD
3/8, 2/4, 1/4 8
1/2, 2/4, 3/5 20
2, 4, 4/3, 5/7 21
5 1/2, 3/2, 7/4, 27/36, 5/20 180