Skip to content
RK Calculator
Menu

Fraction Calculator

Add, subtract, multiply and divide fractions and mixed numbers exactly, simplify a fraction, convert between fractions and decimals, and compare fractions, with step-by-step working.

Change the values and press Calculate to work out your own figures.

Fraction arithmetic

Add, subtract, multiply or divide two fractions or mixed numbers.

Add, subtract, multiply or divide the two values.
First fraction
Second fraction
Result
7/12
Decimal (rounded)
0.5833333333333333
Exact decimal
0.58(3)
Show the working
  1. 3/4 − 1/6
  2. Use the lowest common denominator, 12: 3/4 = 9/12, 1/6 = 2/12
  3. Subtract the numerators: 9 − 2 = 7, so the result is 7/12

Mixed number arithmetic

Type values the way you write them, such as -2 3/4, 5/7, 1.5 or 25%.

A fraction (3/4), mixed number (2 1/2), whole number, decimal (0.75) or percent (75%).
Add, subtract, multiply or divide the two values.
A fraction, mixed number, whole number, decimal or percent.
Result
19/12
Mixed number
1 7/12
Decimal (rounded)
1.583333333333333
Exact decimal
1.58(3)
Show the working
  1. 2 1/3 − 3/4
  2. Write as improper fractions: 2 1/3 = 7/3
  3. Use the lowest common denominator, 12: 7/3 = 28/12, 3/4 = 9/12
  4. Subtract the numerators: 28 − 9 = 19, so the result is 19/12

Simplify a fraction

Reduce a fraction to lowest terms and see it as a mixed number and decimal.

Fraction
Result
3/4
Decimal
0.75
Show the working
  1. Divide top and bottom by their greatest common factor, 6: 18/24 = 3/4

Decimal to fraction

Turn a decimal such as 1.375 into an exact fraction.

A terminating decimal such as 1.375 or -0.125.
Result
11/8
Mixed number
1 3/8
Decimal
1.375
Show the working
  1. 1.375 has 3 decimal places, so write it over 1000: 1375/1000
  2. Divide top and bottom by their greatest common factor, 125: 1375/1000 = 11/8

Fraction to decimal

Turn a fraction into a decimal, showing any repeating digits.

Fraction
Result
0.(285714)
Fraction
2/7
Exact decimal
0.(285714)
Show the working
  1. Divide 2 by 7
  2. The digits in brackets repeat forever: 0.(285714)

Compare two values

Find which of two fractions, decimals or percentages is larger.

A fraction (3/4), mixed number (2 1/2), whole number, decimal (0.75) or percent (75%).
A fraction, mixed number, whole number, decimal or percent.
Result
Comparison
1 2/3 > 25%
1 2/3
5/3 ≈ 1.666666666666667
25%
1/4 ≈ 0.25

1 2/3 is greater than 25%.

Show the working
  1. Write both over a common denominator, 12: 20/12 and 3/12
  2. Compare the numerators: 1 2/3 > 25%

How to use this calculator

Pick what you want to do from the tabs, fill in the boxes and press Calculate. Every result is exact: the calculator works with whole numbers behind the scenes, so 1/3 stays 1/3 instead of turning into 0.333…

  • Arithmetic: enter each fraction as a whole number (optional) and a numerator over a denominator, then choose +, −, × or ÷.
  • Mixed numbers: type values the way you would write them, such as 2 3/4, -5/8, 1.25 or 40%.
  • Simplify: reduce a fraction to lowest terms.
  • Decimal → fraction and Fraction → decimal: convert either way, with repeating digits shown in brackets.
  • Compare: find which of two values is larger, without rounding.

Adding and subtracting fractions

Fractions can only be added or subtracted when they share a denominator, because the denominator says what size the pieces are. The calculator rewrites both fractions over their lowest common denominator, combines the numerators, then reduces the answer.

Worked example: 2 3/4 + 5/6

  1. Turn the mixed number into an improper fraction: 2 3/4 = (2 × 4 + 3)/4 = 11/4.
  2. The lowest common denominator of 4 and 6 is 12.
  3. Rewrite: 11/4 = 33/12 and 5/6 = 10/12.
  4. Add the numerators: 33 + 10 = 43, giving 43/12.
  5. As a mixed number, 43 ÷ 12 is 3 remainder 7, so the answer is 3 7/12.

Multiplying and dividing fractions

To multiply, multiply the numerators together and the denominators together. To divide, flip the second fraction (use its reciprocal) and multiply. Mixed numbers are turned into improper fractions first.

3/4 ÷ 1/6 = 3/4 × 6/1 = 18/4 = 9/2 = 4 1/2

Repeating decimals

A fraction in lowest terms has a decimal that stops only when its denominator has no prime factors other than 2 and 5. Every other fraction repeats forever. The calculator finds the repeating block with long division and puts it in brackets, so 7/12 is shown as 0.58(3) — the 3 repeats. The rounded decimal beside it is limited to 16 significant digits.

Questions

Why does 0.333 not convert to 1/3?

Because 0.333 is exactly 333/1000, which is slightly less than 1/3. Only the endlessly repeating 0.333… equals 1/3. The Compare tab shows the difference: 1/3 is greater than 0.333.

Where does the minus sign go in a mixed number?

A minus sign in front of a mixed number applies to the whole value: -2 3/4 means -(2 + 3/4), which is -11/4, not -2 + 3/4.

Can I use decimals inside a fraction?

Yes. A numerator or denominator such as 1.5 is converted exactly (1.5 = 3/2) before the calculation, so 1.5/7 becomes 3/14.

Reviewed by RK Calculator Team. Updated 2026-09-25.

Formulas

Reduce: divide top and bottom by their greatest common factor
a/b ± c/d = (a × L/b ± c × L/d) / L,  L = lowest common denominator
a/b × c/d = (a × c) / (b × d)
a/b ÷ c/d = (a × d) / (b × c)
n/d = whole number of n ÷ d, remainder over d
0.375 = 375/1000 = 3/8  (write over 10ⁿ, then reduce)
n/d = n ÷ d  (digits in brackets repeat forever)

Sources

Limitations

  • Only two operands per calculation; longer expressions and parentheses are handled by the scientific calculator.
  • Decimal-to-fraction accepts terminating decimals only; a typed 0.333 is treated as exactly 333/1000, not 1/3. Repeating-decimal input notation is not supported.
  • Very large inputs are limited to 100 characters per field; results with more digits are shown in full but repeating decimals are capped at 1000 digits.
  • Fractions of physical measurements (inches, feet-inches) are handled by the inch fraction and length tools.
Cite this calculator

Formula version 0.1.0Reviewed