Reduction
Fraction Simplifier
Simplifying a fraction means dividing its numerator and denominator by their greatest common factor (GCF) until nothing more can be divided out. Type any numerator and denominator below and watch the prime factorization, the GCF, and the reduced result update instantly.
Fraction
Result
View step-by-step working
Method
The Prime-Factorization Method
Worked Example — 86/24
Break the numerator and denominator into prime factors, multiply together whatever primes they share to get the GCF, then divide both parts by it.
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Factor the numerator and denominator
86 = 2 × 43 · 24 = 2 × 2 × 2 × 3
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Find the primes shared by both
Only one 2 in common
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Multiply the shared primes
GCF = 2
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Divide numerator and denominator by the GCF
86 ÷ 2 = 43 · 24 ÷ 2 = 12
86/24 = 43/12
More Examples
Simplifying Fractions of Different Shapes
One division does it
18/24 = 3/4
GCF(18, 24) = 6, so both parts divide down in a single step.
Already in lowest terms
5/9 = 5/9
5 and 9 share no common factor above 1 — there's nothing to divide out.
Even numerator and denominator
8/12 = 2/3
Dividing by 2 alone would only reach 4/6 — the full GCF is 4.
Larger numbers
42/56 = 3/4
GCF(42, 56) = 14.
Numerator divides denominator
7/49 = 1/7
When the numerator is a factor of the denominator, the GCF is the numerator itself.
Negative fraction
−15/40 = −3/8
The sign carries straight through — only the size gets divided by the GCF.
Why It Matters
Why Bother Simplifying at All?
A fraction and its simplified form are never mathematically different quantities — 2/4 and 1/2 land on the exact same point on a number line, and either one is a technically correct way to write that value. What changes is only how easy the number is to read, compare, and work with. Simplest form is the conventional way to report a final answer for exactly that reason: 1/2 communicates the size of the quantity at a glance, while 2/4 forces a reader to notice a shared factor before the size registers.
Teachers, textbooks, and standardized tests treat an un-simplified fraction as an incomplete answer even when the value is correct, because lowest terms is the single canonical way to write any given fraction. There's only ever one simplified form for a value — 2/4, 3/6, and 50/100 all simplify to the same 1/2 — which makes lowest terms the natural way to check whether two fractions that look different are actually equal.
Simplifying also makes every later calculation easier. Comparing 12/18 and 14/21 at a glance is hard; comparing their simplified forms, 2/3 and 2/3, is immediate — they're identical. Adding, multiplying, or converting a fraction to a decimal all involve smaller, easier arithmetic once the numerator and denominator have already been reduced, which is why simplifying is usually the very last step of a calculation rather than something skipped until later.
None of this changes the underlying value being described. Simplifying a fraction is a change in presentation, not a change in size — the same reason a recipe writes "1/2 cup" instead of "50/100 cup" even though both instructions would produce an identical result in the mixing bowl.
Common Mistakes
Where Simplifying Goes Wrong
Quick Reference
Fractions Simplified to Lowest Terms
Search or scroll this table for the simplified form of frequently seen fractions — useful for checking homework or double-checking a mental calculation.
Questions
Frequently Asked Questions
Questions specific to simplifying fractions with prime factorization, not already covered elsewhere on the site.