LCD Calculator: Least Common Denominator
This LCD calculator finds the least common denominator of two or more fractions and rewrites each fraction with that denominator. Type your fractions separated by commas, such as 1/2, 3/4, 5/6, and the tool returns the LCD, the equivalent fractions, their sum in lowest terms and the decimal value. The least common denominator is the smallest number that every denominator divides into evenly, which makes adding and comparing fractions simple. It also lists the prime factors of each denominator so you can follow the method. It works in your browser and accepts whole numbers too.
LCD Calculator
Find the least common denominator of fractions and rewrite them with it.
How to use the LCD Calculator
- Type two or more fractions separated by commas, for example 1/2, 3/4, 5/6.
- Read the least common denominator.
- See each fraction rewritten with the LCD.
- Check the sum in lowest terms and the order from smallest to largest.
- Copy the answer for your homework or notes.
The method
Factor every denominator into primes. Take each prime the greatest number of times it appears in any one denominator and multiply them. That product is the LCD. To rewrite a fraction, multiply its top and bottom by LCD ÷ denominator.
Features
- Any number of fractions
- Equivalent fractions with the LCD
- Sum in lowest terms and decimal
- Fractions sorted from smallest to largest
- Prime factor method shown
- Copy and print
Frequently asked questions
What is the least common denominator?
It is the smallest number that all the denominators divide into evenly. For 1/4 and 1/6 the LCD is 12.
How do I find the LCD?
List the prime factors of each denominator, then multiply each prime the greatest number of times it appears in any denominator. The product is the LCD.
Is the LCD the same as the LCM?
The LCD of fractions is the least common multiple (LCM) of their denominators.
Why do I need a common denominator?
You need the same denominator to add or subtract fractions, and it also makes comparing fractions easy because you only compare the numerators.
Can I enter mixed numbers?
Enter mixed numbers as improper fractions, for example 7/2 for three and a half. Whole numbers such as 3 are treated as 3/1.