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Fraction Reducer – Simplify to Lowest Terms

Quick answer

Reduce any fraction via GCD: 84/126 → GCD 42 → 2/3.

  • Euclid steps, improper fractions and the decimal value 0.667 all shown.

Figures are estimates from this calculator’s standard formula — adjust the inputs in the tool below for your exact number.

How the Fraction Reducer Works

a/b = (a÷g)/(b÷g), g = GCD(a,b) | Euclid: GCD(a,b) = GCD(b, a mod b)

Reducing a fraction divides top and bottom by their greatest common divisor, leaving an equivalent fraction that is easier to read and compute with. For 84/126, Euclid’s algorithm finds the GCD quickly: 126 mod 84 = 42, then 84 mod 42 = 0, so g = 42. Dividing gives 84÷42 = 2 and 126÷42 = 3, hence 2/3. The reducer prints these Euclid steps so the method is transparent, handles improper fractions (99/45 → 11/5) and negatives (−18/24 → −3/4, sign carried on top), and shows the decimal value (2/3 = 0.666…) so you can confirm nothing changed but the form. When the GCD is 1 the fraction is already fully reduced, as with 8/15. Reducing first also prevents overflow when the fraction later feeds into multiplication or addition problems.

  1. 1

    Enter numerator and denominator

    Any integers, including negative or improper fractions

  2. 2

    Run Euclid’s algorithm

    The GCD steps are printed: GCD(84,126) → GCD(126,84)... shows 42

  3. 3

    Divide both parts

    Top and bottom are divided by the GCD

  4. 4

    Confirm equivalence

    The decimal value of both forms is displayed side by side

Use Cases

Homework Cleanup

Turn messy answers like 84/126 into 2/3 before submitting

Cooking Math

A recipe scaled to 12/8 cups reduces to 1½ cups

Probability

Odds like 36/52 simplify to 9/13 for clear reporting

Tips

  • 1

    Divide numerator AND denominator — changing one alters the value

  • 2

    GCD = 1 means the fraction is already in lowest terms

  • 3

    Reducing before multiplying keeps numbers small: (84/126)(10/14) → (2/3)(5/7)

Common Mistakes

  • Dividing only the numerator, silently changing the value

  • Stopping at a common divisor instead of the greatest one: 84/126 → 14/21 → 2/3 wastes a step

  • Dropping the negative sign when reducing −18/24

  • Reducing across an addition: in 1/2 + 1/4 you cannot cancel the 2 and 4

FAQs

What is 84/126 in lowest terms?

GCD(84,126) = 42, so 84/126 = 2/3. Both equal 0.6667.

How does Euclid’s algorithm find the GCD?

GCD(84,126): 126 mod 84 = 42, then 84 mod 42 = 0 — the last nonzero remainder, 42, is the GCD.

Is 8/15 already reduced?

Yes: GCD(8,15) = 1, so no further reduction is possible.

What is 99/45 reduced?

GCD 9: 99/45 = 11/5, an improper fraction equal to 2.2 or 2⅕.

Can I reduce −18/24?

Yes: −18/24 = −3/4. Keep the sign with the numerator.