What does this calculator do?

This calculator adds and subtracts fractions in one expression. Each row represents one fraction, and the operation between rows can be set to plus or minus.

• It supports 2 to 6 fraction rows.
• It works with proper fractions, improper fractions and mixed numbers.
• It finds a common denominator / LCD.
• It simplifies the final result.
• It shows a mixed number form and decimal approximation when useful.

How to enter mixed numbers

A mixed number has a whole part and a fraction part, such as 1 1/2. In the calculator, the whole part is optional, so you can enter either 1/2 or 1 1/2 depending on your problem.

The sign for each fraction row applies to the whole fraction or mixed number. This avoids unclear entries such as a negative whole part with a positive numerator.

Why a common denominator is needed

Fractions with different denominators cannot be added or subtracted directly because their parts are not the same size. One half and one third describe different-sized pieces.

For example, 1/2 + 1/3 becomes 3/6 + 2/6 after using 6 as the common denominator. Then the numerators can be added, giving 5/6.

How the calculation works

1. Convert mixed numbers to improper fractions when needed.
2. Find a common denominator, usually the least common denominator.
3. Rewrite each fraction with that denominator.
4. Add or subtract the numerators according to the selected operations.
5. Simplify the final fraction using the GCD.
6. Show a mixed number form when it helps readability.

The step breakdown is meant to make the common-denominator logic visible, not just to give a final answer.

Simplified result, mixed number and decimal

The simplified result is the main exact fraction result. For example, 6/8 is shown as 3/4 because both numerator and denominator can be divided by 2.

If the result is greater than 1 or less than -1, the calculator may also show a mixed number form. For example, 17/4 can be read as 4 1/4.

The decimal line is an approximation for quick reading. The simplified fraction remains the clearer result when exact fraction form matters.

Examples

• 1/2 + 1/3 = 3/6 + 2/6 = 5/6.
• 1 1/2 + 2 3/4 = 3/2 + 11/4 = 6/4 + 11/4 = 17/4 = 4 1/4.
• 1/2 − 1/4 − 1/8 = 4/8 − 2/8 − 1/8 = 1/8.
• −1/2 + 1/4 uses a negative sign for the first row and gives −1/4.

How to use the calculator

1. Enter at least 2 fraction rows.
2. Use the sign control if a fraction or mixed number is negative.
3. Enter the optional whole part if the value is a mixed number.
4. Enter numerator and denominator as integers.
5. Choose + or − between adjacent rows.
6. Read the simplified result, mixed number, decimal approximation and steps.

Common mistakes

• Adding numerators before making the denominators the same.
• Forgetting to convert a mixed number to an improper fraction.
• Entering 0 as the denominator.
• Putting decimals inside numerator or denominator fields.
• Using separate negative signs instead of the row sign.
• Expecting multiplication or division from this addition/subtraction calculator.

Limitations

This calculator handles addition and subtraction for 2 to 6 fractions. It does not support fraction multiplication, fraction division, variables, algebraic simplification, or unlimited rows.

The calculation is designed for practical and educational fraction work. Very large inputs may be limited by normal calculator safety bounds.