Fraction Calculator
Enter numerators and denominators on the left and pick the operator between fractions; the right pane updates the reduced fraction, decimal, percentage and mixed number right away. Add as many fractions as you need.
Input
Enter numerators and denominators and the result updates automatically.
Result
- Decimal
- —
- Percent
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- Mixed number
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Decimal values are rounded to six places; a zero denominator or division by a zero fraction is treated as an error.
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How to read fraction math at a glance
A fraction calculation means finding a common denominator, doing the arithmetic, and then reading the answer as a reduced fraction plus its decimal, percentage and mixed number. This screen splits that into a left input and a right result and updates as you type.
Numerators and denominators are whole numbers. A zero denominator and division by a zero fraction are treated as errors. Decimals are rounded for display, so very large numbers can show small rounding differences.
The start of fraction math: common denominators and reducing
To add or subtract, find the least common multiple of the denominators, match the denominators, then work on the numerators; at the end, divide by the greatest common divisor to reduce. Multiplication multiplies numerators and denominators; division flips the second fraction and multiplies.
- Add/subtract: common denominator via LCM, then numerators
- Multiply: numerator × numerator, denominator × denominator
- Divide: flip the second fraction and multiply
- Finish: reduce with the greatest common divisor
What to enter and how to read the result
Enter each numerator and denominator on the left and choose the operator (＋, －, ×, ÷) between fractions. Add fraction lets you chain three or more. When values change, the expression, reduced fraction, decimal, percentage and mixed number update immediately.
How reduced fraction, decimal, percent and mixed number relate
The reduced fraction can no longer be simplified. The decimal is numerator divided by denominator, and the percentage is that decimal times 100. The mixed number splits an improper fraction into a whole part and a proper fraction.
- Decimal = numerator ÷ denominator
- Percent = decimal × 100
- Mixed number = whole part + remaining proper fraction
The order when chaining several fractions
With three or more fractions, operators apply left to right. There is no operator precedence where multiplication and division come before addition and subtraction; the input order is followed. If you need precedence, split the calculation into steps.
How negatives and zero are handled
A negative numerator makes a negative fraction, and the sign is kept on the numerator in the result. A zero denominator or dividing by a zero fraction is undefined, so it is reported as an error.
- Negative fraction: sign kept on the numerator
- Zero denominator: cannot calculate (error)
- Divide by a zero fraction: cannot calculate (error)
Input ranges and display
Numerators and denominators are integers. Decimals are rounded to six places with trailing zeros removed, and percentages show two decimals. Very large numerators and denominators are computed within JavaScript integer limits.
Fraction calculator FAQ
What happens if I enter 0 in the denominator?
A fraction denominator cannot be zero. Leaving a denominator at zero or dividing by a zero fraction is treated as a calculation error and no result is shown. Enter a denominator of 1 or more.
How is the reduced fraction calculated?
The numerator and denominator of the answer are divided by their greatest common divisor to form a fraction that cannot be simplified further. Addition and subtraction first use the least common multiple of the denominators, then the result is reduced.
How many fractions can I calculate?
You can add several fractions and the operators apply from left to right. The operator (＋, －, ×, ÷) between each pair is chosen individually, and any fraction you do not need can be removed.
How do the decimal, percentage and mixed number appear?
The decimal is the reduced numerator divided by the denominator, and the percentage is that decimal times 100. The mixed number splits an improper fraction into a whole part and a proper fraction.
Do negative fractions work?
Enter a negative numerator to make a negative fraction. The sign is collected on the numerator and the denominator is kept positive in the result.
Reference date: 2026-07-14. Common denominators, reducing and mixed numbers follow the standard fraction definitions.