Subtracting Fractions Calculator
Subtract fractions with different denominators
How to Subtract Fractions
Find Common Denominator
Find the Least Common Denominator (LCD) of both fractions.
Convert Fractions
Multiply numerator and denominator to match the LCD.
Subtract Numerators
Subtract the second numerator from the first while keeping the denominator.
Simplify
Reduce the fraction to its lowest terms.
Examples
Example 1: Subtract 3/4 − 1/4
Same denominator - just subtract numerators
3/4 − 1/4 = 2/4 = 1/2
Answer: 1/2
Example 2: Subtract 5/6 − 1/3
LCD of 6 and 3 = 6
5/6 = 5/6, 1/3 = 2/6
5/6 − 2/6 = 3/6 = 1/2
Answer: 1/2
Example 3: Subtract 2/3 − 1/4
LCD of 3 and 4 = 12
2/3 = 8/12, 1/4 = 3/12
8/12 − 3/12 = 5/12
Answer: 5/12
About Subtracting Fractions
Subtracting fractions is similar to adding fractions - you need a common denominator before you can subtract. The key difference is you subtract the numerators instead of adding them.
When Denominators Are the Same
If fractions have the same denominator, simply subtract the numerators and keep the denominator. Example: 7/9 − 2/9 = 5/9
When Denominators Are Different
Find the LCD first, convert both fractions to equivalent fractions with that denominator, then subtract the numerators.
Negative Results
If the second fraction is larger than the first, your answer will be negative. For example: 1/4 − 3/4 = -2/4 = -1/2
Real-World Applications
- Cooking: Recipe calls for 3/4 cup, you already added 1/2 cup - how much more? 3/4 − 1/2 = 1/4 cup
- Construction: Board is 7/8 inch, need to remove 1/4 inch - what remains? 7/8 − 1/4 = 5/8 inch
- Time: Task takes 2/3 hour, spent 1/2 hour - how much left? 2/3 − 1/2 = 1/6 hour
Frequently Asked Questions
Why do I need a common denominator?
You can only subtract like quantities. Just as you cannot subtract apples from oranges, you cannot subtract fractions with different denominators without first converting them.
What if the result is negative?
A negative result is perfectly valid! It means the second fraction was larger than the first. Example: 1/4 − 3/4 = -2/4 = -1/2
Can I subtract more than two fractions?
Yes! Find the LCD of all fractions, convert them all, then subtract the numerators in order from left to right.
Do I subtract denominators too?
No! Never subtract the denominators. Only subtract the numerators. The denominator stays the same (after you find a common one).