Fraction Calculator
Add, subtract, multiply and divide fractions and mixed numbers, simplify to lowest terms, and convert between fractions, decimals and percents. Every answer comes with the working, step by step.
Fraction calculator
Add, subtract, multiply or divide two fractions. The answer is shown in lowest terms. Example loaded: 1/2 + 1/3.
Mixed numbers calculator
Add, subtract, multiply or divide mixed numbers. Type the whole number in the first box, or leave it empty for a plain fraction. Example loaded: 1 1/2 + 2 3/4.
Simplify fractions calculator
Reduce a fraction to lowest terms by dividing the top and bottom by their greatest common factor. Example loaded: 18/24.
Decimal to fraction calculator
Turn a decimal into a simplified fraction. Example loaded: 0.375.
Fraction to decimal calculator
Divide the top by the bottom to get a decimal and a percent. Example loaded: 3/8.
Compare fractions calculator
Find out which of two fractions is bigger, or whether they are equal. Example loaded: 3/4 and 5/8.
Quick answer
To add or subtract fractions, give them the same denominator, then add or subtract the numerators. To multiply, multiply across. To divide, flip the second fraction and multiply. Then divide the top and bottom by their greatest common factor to reach lowest terms. For example 1/2 + 1/3 = 3/6 + 2/6 = 5/6.
How to use the calculator
- Scroll to the calculator you need. Each one is on this page, so there is no tab to switch.
- Type your numbers. Whole is optional and is only for mixed numbers.
- The answer updates as you type, with the steps below it.
- Use the steps under each answer to check your working.
Rules at a glance
| Operation | Rule | Example |
|---|---|---|
| Add | Common denominator, add tops | 1/2 + 1/3 = 5/6 |
| Subtract | Common denominator, subtract tops | 3/4 − 1/6 = 7/12 |
| Multiply | Top × top, bottom × bottom | 2/3 × 3/5 = 2/5 |
| Divide | Flip the second, then multiply | 4/3 ÷ 2 = 2/3 |
| Simplify | Divide both by the GCF | 12/18 = 2/3 |
| Mixed to improper | Whole × bottom + top, over bottom | 2 3/4 = 11/4 |
How to add, subtract, multiply and divide fractions
Adding: 2/5 + 3/4
- The denominators are 5 and 4, so the lowest common denominator is 20.
- Rewrite each fraction over 20: 2/5 = 8/20 and 3/4 = 15/20.
- Add the numerators and keep the denominator: 8 + 15 = 23, so the sum is 23/20.
- 23/20 is improper, so the mixed form is 1 3/20.
Subtracting: 7/8 − 1/3
- The lowest common denominator of 8 and 3 is 24.
- Rewrite: 7/8 = 21/24 and 1/3 = 8/24.
- Subtract the numerators: 21 − 8 = 13, so the answer is 13/24. It cannot be simplified.
Multiplying: 3/4 × 2/9
- Multiply the numerators: 3 × 2 = 6. Multiply the denominators: 4 × 9 = 36. That gives 6/36.
- The greatest common factor of 6 and 36 is 6, so 6/36 = 1/6.
- You can also cancel before multiplying: the 3 and the 9 share a factor of 3, which turns 3/4 × 2/9 into 1/4 × 2/3 = 2/12 = 1/6.
Dividing: 3/5 ÷ 2/7
- Keep the first fraction, flip the second one and change ÷ to ×: 3/5 × 7/2.
- Multiply across: 21/10.
- Write it as a mixed number if you need one: 2 1/10.
Worked examples
| Problem | Answer | Mixed | Decimal |
|---|---|---|---|
| 1/2 + 1/3 | 5/6 | — | 0.8(3) |
| 3/4 − 1/6 | 7/12 | — | 0.58(3) |
| 2/3 × 3/5 | 2/5 | — | 0.4 |
| 4/3 ÷ 2 | 2/3 | — | 0.(6) |
| 2 1/3 − 2/3 | 5/3 | 1 2/3 | 1.(6) |
| 1 1/2 + 2 3/4 | 17/4 | 4 1/4 | 4.25 |
| 5/8 ÷ 1/4 | 5/2 | 2 1/2 | 2.5 |
| 2/5 × 3 | 6/5 | 1 1/5 | 1.2 |
Finding the LCD and the greatest common factor
Two ideas do most of the work in fraction arithmetic. The greatest common factor (GCF) is the largest number that divides two numbers exactly. You use it to simplify. The lowest common denominator (LCD) is the smallest number both denominators divide into. You use it to add, subtract and compare.
GCF of 24 and 36
Divide the larger by the smaller and keep the remainder: 36 = 1 × 24 + 12. Then 24 = 2 × 12 + 0. The last non-zero remainder, 12, is the GCF. So 24/36 simplifies to 2/3.
LCD of 6 and 8
Multiply the two numbers and divide by their GCF. The GCF of 6 and 8 is 2, so the LCD is 6 × 8 ÷ 2 = 24. Using 24 instead of the plain product 48 keeps the numbers small and the answer easier to simplify.
Mixed numbers and improper fractions
A mixed number is a whole number plus a proper fraction, such as 2 3/4. An improper fraction has a top that is not smaller than the bottom, such as 11/4. To convert up, multiply the whole by the denominator and add the numerator. To convert back, divide the top by the bottom: the quotient is the whole and the remainder is the new numerator. Calculations are easiest on the improper form, which is what the steps use.
Comparing and ordering fractions
The quickest check for two fractions is cross-multiplication. To compare 3/4 with 5/8, multiply across: 3 × 8 = 24 and 5 × 4 = 20. The larger product sits on the side of the larger fraction, so 3/4 is greater than 5/8.
To put three or more in order, put them all over the same denominator. For 2/3, 3/4 and 5/8, use 24: they become 16/24, 18/24 and 15/24. From smallest to largest the order is 5/8, 2/3, 3/4.
Fractions, decimals and percents
| Fraction | Decimal | Percent |
|---|---|---|
| 1/2 | 0.5 | 50% |
| 1/3 | 0.(3) | 33.33% |
| 1/4 | 0.25 | 25% |
| 1/5 | 0.2 | 20% |
| 1/8 | 0.125 | 12.5% |
| 2/3 | 0.(6) | 66.67% |
| 3/4 | 0.75 | 75% |
A fraction ends as a decimal only when its lowest-terms denominator has no prime factors other than 2 and 5. Anything else repeats.
Fraction word problems
Scaling a recipe
A recipe needs 3/4 cup of flour and you want to make 1 1/2 batches. Multiply 3/4 × 3/2 = 9/8, which is 1 1/8 cups.
Cutting a board
A board is 5 1/2 metres long and each piece needs to be 3/4 of a metre. Divide: 11/2 ÷ 3/4 = 11/2 × 4/3 = 22/3, which is 7 1/3. You get 7 full pieces, with 1/3 of a piece left over. That leftover is 1/4 of a metre.
In both cases, turn mixed numbers into improper fractions before you multiply or divide, and turn the answer back into a mixed number at the end.
How to do fractions on a calculator
Most scientific calculators have a fraction key, often marked a b/c or with a small box-over-box symbol. The exact keys differ by model, so check your manual if yours looks different.
- Type the numerator, press the fraction key, then type the denominator. For 3/4 you press 3, the fraction key, 4.
- For a mixed number such as 2 1/3, type the whole number, press the fraction key, type the numerator, press it again, then type the denominator.
- Use the plus, minus, multiply and divide keys as normal, then press equals.
- Many models have an S⇔D key or a shift function that switches the answer between a fraction, a decimal and a mixed number.
Phone calculators usually have no fraction key. Divide the numerator by the denominator to get a decimal, then type that decimal into the Decimal to fraction calculator on this page to get the lowest terms and the working.
Common mistakes
- Adding the denominators. 1/2 + 1/3 is not 2/5.
- Forgetting to flip the second fraction when dividing.
- Cross-cancelling while adding. That shortcut works only for multiplication.
- Leaving the answer unsimplified, or turning a negative mixed number into a mix of signs.
Frequently asked questions
Can I add a whole number and a fraction?
Yes. Put the whole number in the Whole box and leave the numerator and denominator empty. For 3 + 1/4, type 3 in Whole for the first fraction, then 1 and 4 for the second.
Does it work with negative fractions?
Yes. Put the minus sign in front of the whole number or the numerator, for example −3/4 or −2 in Whole. A negative mixed number is read as one negative value, so −2 1/2 means −2.5.
What happens if the denominator is zero?
Nothing can be divided by zero, so the calculator shows a message instead of an answer. Dividing by a fraction whose value is zero, such as 0/5, gives the same message.
How big can the numbers be?
Very big. The maths uses exact whole-number arithmetic, so fractions stay exact instead of turning into rounded decimals. The calculators accept whole numbers up to 1 billion. For anything larger, or when an answer would be too large to stay exact, they ask you to use smaller numbers.
How do I find a fraction of an amount, like 3/4 of 80?
Choose Multiply, enter 3/4 as the first fraction and 80 in Whole of the second. The answer is 60.
Why does the answer sometimes show a mixed number and sometimes not?
A mixed number only exists when the fraction is larger than 1 and not a whole number. 7/4 is 1 3/4. 3/4 and 8/4 have no mixed form, so that card is skipped.
What do the brackets in a decimal mean?
Brackets mark the digits that repeat forever. 5/6 is 0.8(3), which means 0.8333 and so on. You can type the same form in the Decimal to fraction calculator.
How do I compare two fractions?
Use the Compare fractions calculator on this page. It puts both over a common denominator and tells you which is larger and by how much. 3/4 against 5/8 gives 6/8 against 5/8, so 3/4 is bigger by 1/8.
Is this the same as a handheld fraction calculator?
The answers are the same. The difference is the working: every operation here lists the steps, so you can copy them into homework or check your own method.
Is my data saved?
No. Everything is worked out in your browser and nothing you type is sent or stored.
About this calculator
The fraction calculator handles proper, improper and mixed fractions, negatives and decimals, and shows the working. It runs entirely in your browser and is free to use.
Who wrote this
Written and reviewed by Umar Khan, PhD student in engineering at NTNU. Last updated 3 November 2026.