Fraction Subtraction Calculator

Subtract Two Fractions

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This calculator subtracts two fractions. It accepts proper, improper, mixed fractions and whole number inputs. If they exist, the solutions and answers are provided in simplified, mixed and whole formats.

There general steps to subtract fractions are described below.
  • If the inputs are mixed fractions or whole numbers, convert them to improper fractions.
  • Determine the Least Common Multiple (LCM).
  • Multiply the left and right fractions by a factor so each of the fractions have the LCM as the denominator.
  • Subtract the left and right numerators. This will be the numerator of the final answer.
  • The denominator of the final answer is simply the LCM.
  • Simplified and Mixed Number Answers:
  • Find the Greatest Common Divisor (GCD)
  • Divide the answer's numerator and denominator by the GCD to get the simplified solution.
  • If the answer is greater than one, then a mixed solution exists. Simply divide the numerator by the denominator. The mixed number's whole part is self explanatory. The mixed number's fraction is the remainder over the original denominator.

Instructions/How To

This calculator will automatically update the answer or solution when any of the inputs change. The inputs include the whole number, numerator or denominator inputs fields.
  • Select the type of fraction or whole number. Do not select either field for improper or proper factions. This is the default. Selected Mixed for mixed fractions and whole for whole numbers.
  • Enter the left fraction. This the fraction to the left of the subtraction operand.
  • Enter the right fraction. This is the fraction to the right of the operand.
  • Observe the step by step solution and various answers.
Note: If viewing this page on a desktop or laptop, the numerator and denominator inputs can be changed with the mouse wheel, up and downs spinner buttons and keyboard arrow keys. The mobile and smart phone version does not support these options.


Parameter Type Description
Left Fraction Not applicable Refers to the fraction or number which is left of the subtraction sign.
Right Fraction Not applicable Refers to the fraction or number which is right of the subtraction sign.
Mixed Check Box Select to enter an mixed fraction or number. This is a number with a whole number, numerator and denominator.
Whole Check Box Select to enter a whole number. This is a number with only a whole number.
Whole Edit Box The whole part of the mixed fraction or number. This is restricted to integer values.
Numerator Edit Box The upper or top part of the fraction. This is restricted to integer values.
Denominator Edit Box The lower or bottom portion of the fraction. This is restricted to integer values.


Parameter Description
Improper Conversion If the fraction is mixed, the steps to convert to an improper fraction are displayed.
Improper Fraction If the fraction is mixed, the values of the final improper fraction.
Subtract Shows the actual subtraction steps.
Least Common Multiple (LCM) Shows the computed Least Common Multiple. This is the smallest number in which both fractions will evenly divide.
Answer Shows the solution. Note, this solution is not simplified.
Greatest Common Divisor This is used to simplify the answer. The biggest or largest integer value which will divide the numerator and denominator without producing a fraction.
Divide By GCD Shows the numerator and denominator being divided by the GCD to reduce the fraction.
Answer (Simplified) The solution in proper or improper format.
Answer (Mixed) If the solution is an improper fraction, the converted mixed fraction is displayed. The mixed fraction show the fraction with the whole part in subtraction to the left over part of the fraction.

Error Messages

Parameter Description
Invalid Input This error is displayed when the numerator or denominator has any of the following conditions:
1) The field is blank or empty.
2) The field contains a string which not an integer value.
3) Any value in the calculations exceeds 900000000000000.

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Copyright 2012 by Jimmy Raymond