Add the numerators together and keep the denominator exactly as it is. Do not add the denominators. The denominator describes the size of the pieces, and that size does not change just because you are combining more of them.
Add two, three, four, or five fractions at once, even with completely unlike denominators. Every keystroke instantly updates the least common denominator, the equivalent fractions, and the simplified sum, so you can see exactly how the answer is built instead of just what it is.
Enter 2 to 5 fractions. Switch to Mixed to add whole-number parts.
Fractions can only be added once they are measured in the same-size pieces. When two fractions have different denominators, you cannot add the numerators directly. A slice that is one-fourth of a pizza is not the same size as a slice that is one-sixth of a pizza. The fix is a three-step process that rewrites every fraction using a shared denominator before anything gets added.
Find the least common denominator of every denominator in the problem. It is the smallest number each denominator divides into evenly.
Multiply each fraction's numerator and denominator by the factor that turns its denominator into the LCD.
Add the new numerators over the shared denominator, then simplify and convert to a mixed number if needed.
For example, to add 1/4 and 1/6, the LCD of 4 and 6 is 12. Multiplying 1/4 by 3/3 gives 3/12, and multiplying 1/6 by 2/2 gives 2/12. Adding those numerators gives 3/12 + 2/12 = 5/12, which is already in lowest terms.
When every fraction in the problem already shares the same denominator, the LCD step disappears entirely. The denominator is already common, so there is nothing left to convert.
Add the numerators together and keep the denominator exactly as it is. Do not add the denominators. The denominator describes the size of the pieces, and that size does not change just because you are combining more of them.
3/8 + 2/8 = (3 + 2)/8 = 5/8. The denominator stays 8 throughout; only the numerators combine. If the result can be simplified, such as 4/8 + 2/8 = 6/8, reduce it afterward to 3/4.
A mixed number such as 1 1/2 combines a whole number and a fraction. To add mixed numbers correctly, convert each one into an improper fraction first, so the whole-number part cannot get lost or mishandled during the addition.
Notice that the whole-number parts (1 and 2) are folded into the improper fractions before any addition happens. Adding the whole numbers and fraction parts separately can work for simple cases, but it breaks down the moment a "carry" is needed, for example when the fraction parts add up to more than one whole. Converting to improper fractions first avoids that pitfall entirely.
Each example below shows the same three steps used by the calculator above: find the LCD, convert to equivalent fractions, then add the numerators and simplify.
Most addition errors trace back to one of these four habits. Watching for them is often enough to catch a wrong answer before it happens.
1/4 + 1/6 is not 2/10. Denominators describe the size of the pieces, not a quantity to be summed. You must find a common denominator, ideally the LCD, before the numerators can be combined.
An answer like 6/8 is correct but incomplete. It should be reduced to 3/4. Always divide the numerator and denominator by their greatest common factor as a final step.
Adding whole numbers and fraction parts separately can silently produce the wrong total whenever the fractions add up to more than one. Convert every mixed number to an improper fraction before adding.
1/2 + 1/2 is 1, not 2/4. Once the denominators match, only the numerators are added; the shared denominator is written once, underneath the new numerator.