Simplify 18/21

18/21 simplified is 6/7, after dividing the top and bottom by 3.

Result

Answer

\frac{18}{21} = \textcolor{#0b5c56}{\frac{6}{7}}

18/21 simplifies to 6/7.

  • Greatest common factor: 3
  • Decimal: \displaystyle 0.\overline{857142} (the 857142 repeats forever, about 0.8571)
  • Percent: 85.71%
18/216/7

Same amount, fewer parts

Step-by-step solution

The problem

\frac{18}{21}

  1. Find the greatest common factor. List the factors of each:
    Factors of 18: 1, 2, 3, 6, 9, 18
    Factors of 21: 1, 3, 7, 21
    The greatest common factor (GCF) is 3.

    \text{GCF}(18, 21) = 3

  2. Divide the top and bottom by 3. Dividing both by the same number keeps the value the same.

    = \frac{18 \div 3}{21 \div 3} = \textcolor{#0b5c56}{\frac{6}{7}}

All the working together

\begin{aligned} &\frac{18}{21} \\[8pt] &= \frac{18 \div 3}{21 \div 3} && \textcolor{#5b6660}{\textsf{divide by 3}} \\[8pt] &= \textcolor{#0b5c56}{\frac{6}{7}}\end{aligned}

18/21 in other forms

Simplest form6/7
Greatest common factor3
Decimal0.857142… (the 857142 repeats forever)
Percent≈ 85.71%
Equal fractions12/14, 24/28, 30/35, 36/42

Fractions over 21 simplified

FractionSimplest formDecimal
1/21already simplest0.047619…
2/21already simplest0.095238…
3/211/70.142857…
4/21already simplest0.190476…
5/21already simplest0.238095…
6/212/70.285714…
7/211/30.333…
8/21already simplest0.380952…
9/213/70.428571…
10/21already simplest0.476190…
11/21already simplest0.523809…
12/214/70.571428…
13/21already simplest0.619047…
14/212/30.666…
15/215/70.714285…
16/21already simplest0.761904…
17/21already simplest0.809523…
18/216/70.857142…
19/21already simplest0.904761…
20/21already simplest0.952380…

Frequently asked questions

What is 18/21 in simplest form?

18/21 simplifies to 6/7. Divide the top and bottom by 3, their greatest common factor: 18 ÷ 3 = 6 and 21 ÷ 3 = 7.

What is the greatest common factor of 18 and 21?

The GCF of 18 and 21 is 3 – the biggest number that divides both with nothing left over.

Is 18/21 equal to 6/7?

Yes. Both are 0.857142… (≈ 85.71%). Simplifying changes how the fraction is written, not its value.

More fractions to simplify

Any other fraction or mixed number: use the Simplify Fractions Calculator.