Math · fractions
Add fractions without the guesswork.
Add, subtract, multiply or divide fractions and mixed numbers. The answer is simplified automatically, with the decimal value alongside.
Two fractions
Fractions, mixed numbers and decimals are accepted.
Try one
Result
1 1/4
1/2 + 3/4 = 1.25
Decimal
1.25
Rounded to six places
Improper
5/4
Before mixed-number formatting
How the answer is simplified
The calculator multiplies denominators to combine the fractions, then divides the numerator and denominator by their greatest common divisor. A result with a larger numerator than denominator is shown as a mixed number, alongside the improper form.
A negative sign on a mixed number applies to the whole value: −1 1/2 means −1.5.
How it works
How fraction arithmetic stays exact
Fractions are exact numbers, but they need a common denominator before they can be added or subtracted. This calculator does that work and then reduces the answer, so the result is both correct and easy to read.
Common denominators
To add or subtract, both fractions must describe the same size of piece. Multiplying each numerator by the other denominator creates a common denominator without guessing the lowest one. The result is then reduced by the greatest common divisor.
Mixed numbers and signs
A mixed number such as 1 1/2 is converted to the improper fraction 3/2 before the operation. A leading minus sign applies to the whole value, so -1 1/2 becomes -3/2, not -1/2. Keeping the sign in the numerator avoids confusing negative denominators.
Decimals and rounding
A decimal input is turned into a fraction using its decimal places, so 0.75 becomes 75/100 and then 3/4. The arithmetic is exact for the values you enter. Only the displayed decimal result is rounded, and it is shown to six places.
Good to know
The result is a guide, not a guarantee.
This calculator runs entirely in your browser. Check the assumptions, keep the inputs realistic, and use the result as a starting point for a decision.
Results are exact for the fractions you enter; only the displayed decimal is rounded.
How do I enter a mixed number?
Type the whole number, a space, then the fraction, such as 1 1/2. A leading minus sign applies to the whole value: -1 1/2 means -1.5. Decimals such as 0.75 are accepted too.
Why is the answer shown as a mixed number?
When the simplified numerator is larger than the denominator, the result is easier to read as a whole number plus a fraction. The improper fraction is shown beside it, because that form is often more useful for further algebra.
Does the calculator simplify the result?
Yes. Every result is reduced by dividing the numerator and denominator by their greatest common divisor, and the sign is moved to the numerator so the denominator stays positive.
Can I use decimals instead of fractions?
Yes. A decimal is converted to an exact fraction using its number of decimal places, up to six places. Numbers with more places are rounded before the calculation, so use fraction notation when you need exact repeating values.
Why can I not divide by zero?
Division by zero is undefined in arithmetic. The calculator checks the second fraction before dividing and shows an error instead of returning a meaningless result.
Is the calculator free and private?
Yes. It needs no account, runs entirely in your browser, and the numbers you enter are not sent to simplytools.us or any third party.