Subtract fractions with unlike denominators using the LCD method. Supports mixed numbers, borrowing, step-by-step solution table, visual fraction bars, and presets.
The **Subtracting Fractions Calculator** subtracts any two fractions — including those with unlike denominators and mixed numbers — using the least common denominator (LCD) method. Every step is shown in a clear table so you can follow exactly how the answer is found.
Subtracting fractions is trickier than multiplying or dividing them because you first need a common denominator. The LCD is the smallest number that both denominators divide into evenly. Once both fractions share the same denominator, you simply subtract the numerators and keep the denominator. This calculator finds the LCD automatically and shows how each fraction is scaled.
Mixed numbers add another layer of complexity. When the fraction part of the first mixed number is smaller than the second, you need to borrow 1 from the whole number and add it to the fraction part. This calculator handles borrowing automatically and explains the process in the steps table.
The visual fraction bars give you an intuitive feel for the subtraction: you can see the first fraction, the second fraction, and the resulting difference side by side. A reference table of common subtraction problems is included at the bottom — click any row to load it into the calculator. Use the preset buttons for quick access to popular problems.
Fraction subtraction is where many learners start making denominator mistakes. This calculator makes the LCD step explicit, shows the converted equivalent fractions, and keeps the simplified difference tied to the paper method students are expected to use.
It is also useful for mixed numbers, where borrowing can be hard to visualize. The steps table shows how the whole-number part is adjusted before subtraction, and the visual bars help confirm whether the result should be a small positive fraction, a larger mixed number, or a negative value.
a/b − c/d = (a×(LCD/b) − c×(LCD/d)) / LCD, where LCD = LCM(b, d)
Result: 5/6 - 1/4 = 7/12.
Use an LCD of 12. Then 5/6 becomes 10/12 and 1/4 becomes 3/12, so the difference is 10/12 - 3/12 = 7/12.
The numerators can only be subtracted directly when both fractions are measured in the same-sized parts. The least common denominator creates that shared unit, which is why 5/6 - 1/4 must first become 10/12 - 3/12.
When the fractional part of the top mixed number is smaller than the fractional part being subtracted, you borrow 1 from the whole-number part and rewrite it as extra fractional pieces. That keeps the value equivalent while making the subtraction possible.
If the second fraction is visibly larger than the first, the result should be negative. The fraction bars and decimal output give a quick sanity check before you rely on the simplified fraction alone.
Find the least common denominator (LCD), convert both fractions to equivalent fractions with that denominator, then subtract the numerators. The shared denominator makes the subtraction valid because both values are measured in the same-sized pieces.
The least common denominator is the smallest number that both denominators divide into evenly. It equals LCM(b, d) = b × d / GCD(b, d), which is the same as the least common multiple of the denominators.
Convert to improper fractions, find the LCD, subtract, then convert back to a mixed number. Alternatively, subtract whole parts and fraction parts separately, borrowing if needed, which can be easier for hand calculation.
When the fraction part being subtracted is larger, borrow 1 from the whole number and add it to the fraction. E.g. 3 1/4 − 1 3/4: borrow to get 2 5/4 − 1 3/4 = 1 2/4, which then simplifies to 1 1/2.
Yes. If the second fraction is larger than the first, the difference will be negative. The calculator handles this correctly, so the sign still reflects the subtraction order.
If the denominators are already the same, no conversion is needed. Just subtract the numerators directly and keep the denominator, because the fractions are already in like units.
Divide the numerator and denominator by their GCD. The calculator simplifies automatically, but the same reduction keeps the fraction in lowest terms by hand.