The least common denominator is the smallest number every denominator divides into. Using it to add or compare fractions keeps the numbers as small as possible.
How to use the LCD Calculator – Least Common Denominator
- Number of fractions
- Fraction form
- Fraction 1: whole
- Fraction 1: numerator
- Fraction 1: denominator
- Fraction 2: whole
- Fraction 2: numerator
- Fraction 2: denominator
- Fraction 3: whole
- Fraction 3: numerator
- Fraction 3: denominator
- Fraction 4: whole
- Fraction 4: numerator
- Fraction 4: denominator
- Fraction 5: whole
- Fraction 5: numerator
- Fraction 5: denominator
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How it works
Each fraction is simplified, then the least common multiple of the denominators is found. Every fraction is scaled up to that denominator.
Formula
LCD = LCM(d₁, d₂, …, dₖ)
Worked example
Inputs — Number of fractions: 2; Fraction form: Simple fraction; Fraction 1: numerator: 1; Fraction 1: denominator: 4; Fraction 2: numerator: 5; Fraction 2: denominator: 6.
Results — Least common denominator = 12; Equivalent fractions = 1/4 = 3/12
5/6 = 10/12; Steps = Denominators (after simplifying): 4, 6
The LCD is the least common multiple of the denominators: 12.
Key terms
- Least common denominator
- The smallest common multiple of the denominators.
Frequently asked questions
What is the LCD of 1/4 and 5/6?
12.
Is the LCD the same as the LCM?
The LCD is the LCM of the denominators.
Can I just multiply the denominators?
That gives a common denominator, but not always the least one.
Why simplify fractions first?
A simplified fraction may need a smaller common denominator.