LCD Calculator
Enter two or more fractions below (like 1/4, 1/6) to instantly find their least common denominator, with each fraction converted to it.
What Is the LCD?
The least common denominator (LCD) of two or more fractions is the smallest number that all of their denominators divide into evenly — in other words, it's just the least common multiple (LCM) applied to the denominators. Once every fraction shares this denominator, they can be added or subtracted directly.
How to Find and Use the LCD, Step by Step
- Find the LCM of all the denominators — that's the LCD.
- For each fraction, divide the LCD by its original denominator to get a multiplier.
- Multiply both the numerator and denominator of that fraction by the multiplier.
- Every fraction now shares the same denominator and can be added or subtracted directly.
Worked example
Add 1/4 and 1/6.
LCD of 4 and 6 = LCM(4, 6) = 12
1/4 → multiply by 3/3 → 3/12
1/6 → multiply by 2/2 → 2/12
3/12 + 2/12 = 5/12
Frequently Asked Questions
What is the LCD of two fractions?
The least common denominator (LCD) is the smallest number that can serve as a common denominator for two or more fractions. It's simply the least common multiple (LCM) of the fractions' denominators.
Why do you need the LCD?
You can only add or subtract fractions once they share the same denominator. Using the least common denominator, rather than any common denominator, keeps the numbers as small as possible and avoids extra simplifying at the end.
How do you convert a fraction to the LCD?
Divide the LCD by the fraction's original denominator to get a multiplier, then multiply both the numerator and denominator by that multiplier. This changes how the fraction looks but not its value.
Is the LCD always bigger than the original denominators?
Not necessarily — if one denominator is already a multiple of the others, the LCD equals the largest denominator. For example, the LCD of 1/4 and 3/8 is 8, since 8 is already a multiple of 4.
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- LCM Calculator — General Math
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