Enter whole-number-and-fraction combinations directly. No need to convert them by hand first. This calculator turns every mixed number into an improper fraction automatically, finds the least common denominator of the group, and hands the answer back to you in mixed-number form.
Leave the whole-number box at 0 to enter a plain fraction.
Steps will appear here once your mixed numbers are entered.
A mixed number combines a whole number and a proper fraction into a single value, such as 1 3/4 pizzas or 2 1/2 miles. It is the everyday way people describe quantities that are more than a whole unit but not a clean multiple of one, such as a recipe that calls for 2 1/3 cups of flour, a board that measures 5 5/8 inches, or a race that finishes in 1 1/4 hours. Mixed numbers sit between whole numbers on the number line, and every mixed number has an equal improper-fraction twin that represents exactly the same amount.
Every mixed number has a whole-number part and a fractional part, written side by side. In 1 3/4, the "1" tells you there is one complete whole, and the "3/4" tells you how much of a second whole is included beyond that. The fractional part is always a proper fraction, meaning its numerator is smaller than its denominator, because once the fraction part reaches or passes a whole, it gets folded into the whole-number count instead.
A mixed number is only written that way because the fraction part is less than one whole. If the fraction reaches 4/4 or higher, it converts into another whole unit, so 1 4/4 is always renamed 2, and 2 5/4 is always renamed 3 1/4. Keeping the fractional part proper is what makes mixed numbers easy to read at a glance. You instantly know how many whole units you have and roughly how much extra, which is exactly why recipes, rulers, and clocks favor mixed numbers over raw improper fractions.
Before you can find a least common denominator across mixed numbers, every one of them needs to become a single fraction. That single fraction is called an improper fraction because its numerator is allowed to be larger than its denominator. It represents the same value as the mixed number, just without the whole-number part split out separately.
Multiply the whole number by the denominator, then add the numerator. The denominator itself never changes during this step. Only the numerator grows to absorb the whole-number value.
Once every mixed number in your problem is rewritten this way, you are simply left with a group of ordinary fractions, and finding their least common denominator works exactly the same as it would for any other set of fractions.
Finding a shared denominator across several mixed numbers is a three-step routine. Skip the first step and it is easy to scale a numerator against the wrong whole-number value, so always convert before comparing denominators.
If you tried to find a common denominator while the whole-number parts were still attached, you would have nowhere to put the extra value once you multiplied the fraction up. The whole number and the fraction would drift out of sync. Converting to a single improper fraction first keeps the whole quantity glued together as one number, so scaling it to a new denominator never loses or duplicates any value.
Once every mixed number shares the same denominator, addition and subtraction become simple: combine the numerators, keep the denominator, and simplify. These two worked examples show the full path from mixed numbers to a final mixed-number answer.
Each example below converts mixed numbers to improper fractions, finds the LCD, and reconverts the sum back into mixed-number form.