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LCD Calculator (Least Common Denominator)

Before you can add, subtract, or compare fractions with different bottom numbers, you need a common denominator. The Least Common Denominator (LCD) is simply the Least Common Multiple of the denominators. Enter your fractions below to convert and add them automatically.

Least Common Denominator
Least Common Denominator (LCD)
LCD(6, 8, 12) = 24

Step 1: Rewrite Each Fraction with Denominator 24

1/6 = (1 × 4) / (6 × 4)= 4/24
3/8 = (3 × 3) / (8 × 3)= 9/24
5/12 = (5 × 2) / (12 × 2)= 10/24

Step 2: Add the Equivalent Fractions Together

4/24 + 9/24 + 10/24 = 23/24

How to Convert Fractions Using the LCD (3 Steps)

  1. Find the LCM of the denominators: For 1/6 and 3/8, the denominators are 6 and 8. Their Least Common Multiple is 24.
  2. Find each fraction's multiplier: Divide the LCD by each old denominator (24 ÷ 6 = 4 and 24 ÷ 8 = 3).
  3. Multiply top and bottom by that multiplier: 1/6 = (1×4)/(6×4) = 4/24, and 3/8 = (3×3)/(8×3) = 9/24. Now you can add the numerators straight across: 4/24 + 9/24 = 13/24.

Want to find the LCM of the entire fractions themselves (not just the denominators)? Read our LCM of Fractions Formula Guide.