Quick start
- Choose Arithmetic, Simplify / convert, or Compare.
- Enter fractions as separate whole, numerator, and denominator boxes in Arithmetic.
- Type values such as 3/4, -2 1/4, 7, or 0.125 in the other two modes.
- Run the calculation and read the headline result.
- Check the improper fraction, decimal, percentage, LCD, cross-products, or reduction steps before copying.
Choose the mode that matches the question
Arithmetic: add, subtract, multiply, or divide two fractions or mixed numbers.
Simplify / convert: reduce one value and show fraction, mixed-number, decimal, percentage, and equivalent forms.
Compare: tell whether the first exact value is greater than, less than, or equal to the second.
Arithmetic combines two values. Simplify / convert works on one value. Compare checks the exact relation between two values with cross-products.
Arithmetic mode for two fractions
Leave Whole blank for a simple fraction. For 2 1/4, enter 2 in Whole, 1 in Numerator, and 4 in Denominator. Choose the operation after both values are filled in.
Why the least common denominator helps
Addition and subtraction need equal-sized parts. The least common denominator is the least common multiple of the two denominators. For 1/4 + 1/6, the LCD is 12. Rewrite the inputs as 3/12 and 2/12, then add them to get 5/12.
Multiplying the denominators would also produce a common denominator, but 24 is larger than needed. Showing the LCD keeps the working numbers smaller and matches the usual classroom method.
Simplify fractions and convert decimals
Simplify / convert accepts one fraction, mixed number, whole number, or terminating decimal. It keeps the calculation exact by using integers rather than converting everything through rounded decimal math.
Divide both parts by 6 to get 3/4.
Shows 9/4, 2.25, and 225%.
Write 125/1000, then simplify to 1/8.
A typed decimal is treated as terminating and may use up to nine decimal places. For an exact repeating value, enter the fraction itself. Use 1/3 instead of a rounded string of threes.
Compare fractions without rounding
Compare mode turns both inputs into exact fractions and cross-multiplies. For 2/3 and 3/5, compare 2 x 5 with 3 x 3. Since 10 is greater than 9, 2/3 is greater than 3/5.
The result also shows both decimals and the exact difference. Equal values stay equal even when they are written differently, so 3/4 and 6/8 return an equals sign.
Examples available in the calculator
5/6
1 7/8
3/10
1 1/4
3/4
1/8
2/3 > 3/5
Common mistakes to check
- A denominator cannot be zero.
- In Arithmetic, keep a mixed number's whole part in the Whole box.
- In the text modes, put one space between a whole number and its fraction, as in 2 1/4.
- For subtraction and comparison, swapping the first and second values can change the sign or direction.
- Do not treat a rounded repeating decimal as the exact fraction.
- For a three-value problem, preserve the original order of operations when carrying one result into the next step.
When another calculator is better
Use the LCM Calculator when you only need a common multiple. Use the GCF Calculator when you only need a shared factor. Use the Percentage Calculator for percent-of, percentage change, discount, or reverse-percentage questions.
Research and references
OpenStax explains fraction forms and mixed-number operations. Its unlike-denominator lesson defines the least common denominator as the least common multiple of the denominators.
Quick questions
Which mode should I use?
Use Arithmetic for an operation between two fractions. Use Simplify / convert for one fraction, mixed number, whole number, or terminating decimal. Use Compare when you need greater than, less than, or equal to.
Why does addition use the least common denominator?
The LCD is the smallest denominator that both fractions can use. It keeps the equivalent-fraction step smaller and easier to check than multiplying the denominators every time.
Can I turn 0.125 into a fraction?
Yes. Simplify / convert writes 0.125 as 125/1000 and divides both parts by 125, giving 1/8.
Can I enter a repeating decimal?
Enter the exact fraction instead. A typed decimal is treated as a terminating value with no more than nine decimal places, so 0.333 is not exactly one third.
How does fraction comparison stay exact?
The calculator converts both inputs to fractions and cross-multiplies. That avoids deciding from rounded decimal displays.
Can I calculate three fractions at once?
The Arithmetic mode works with two values at a time. Calculate the first pair, then use the simplified answer as one input for the next operation. Keep the order of operations from the original problem.
History, privacy, and copying
Recent answers stay in the current browser tab while you calculate, simplify, or compare values. They are not sent to a server.
Copy answer includes enough context to identify the input and result. Check the mode, signs, and requested answer form before pasting it into homework, recipe notes, measurements, or a spreadsheet.