Mathwords logoMathwords

Converting Percents and Fractions — Definition, Formula & Examples

Converting percents and fractions means rewriting a percent as a fraction or rewriting a fraction as a percent. Since "percent" means "per hundred," every percent can be written as a fraction with 100 in the denominator, and every fraction can be turned into a percent by finding its equivalent value out of 100.

A percent p%p\% is equivalent to the fraction p100\dfrac{p}{100}, which may then be simplified to lowest terms. Conversely, a fraction ab\dfrac{a}{b} is converted to a percent by computing ab×100%\dfrac{a}{b} \times 100\%.

Key Formula

p%=p100andab=ab×100%p\% = \frac{p}{100} \qquad \text{and} \qquad \frac{a}{b} = \frac{a}{b} \times 100\%
Where:
  • pp = The percent value (e.g., 75 in 75%)
  • aa = The numerator of the fraction
  • bb = The denominator of the fraction

How It Works

To convert a percent to a fraction, write the percent value over 100 and simplify by dividing the numerator and denominator by their greatest common factor. For example, 45%45\% becomes 45100\frac{45}{100}, which simplifies to 920\frac{9}{20}. To convert a fraction to a percent, divide the numerator by the denominator, then multiply the result by 100. Alternatively, you can find an equivalent fraction with a denominator of 100 — the numerator then equals the percent. Both directions rely on the core idea that "percent" literally means "out of one hundred."

Worked Example

Problem: Convert 60% to a fraction in simplest form.
Step 1: Write the percent over 100.
60%=6010060\% = \frac{60}{100}
Step 2: Find the greatest common factor (GCF) of 60 and 100. The GCF is 20.
gcd(60,100)=20\gcd(60, 100) = 20
Step 3: Divide both the numerator and denominator by 20 to simplify.
60÷20100÷20=35\frac{60 \div 20}{100 \div 20} = \frac{3}{5}
Answer: 60%=3560\% = \dfrac{3}{5}

Another Example

Problem: Convert the fraction 7/8 to a percent.
Step 1: Divide the numerator by the denominator.
7÷8=0.8757 \div 8 = 0.875
Step 2: Multiply the decimal result by 100 to get the percent.
0.875×100=87.50.875 \times 100 = 87.5
Step 3: Attach the percent symbol.
78=87.5%\frac{7}{8} = 87.5\%
Answer: 78=87.5%\dfrac{7}{8} = 87.5\%

Visualization

Why It Matters

Converting between percents and fractions shows up constantly in pre-algebra, statistics, and everyday life — from calculating sales tax and tip amounts to interpreting test scores. In science courses, you often need to express experimental data as either a fraction or a percent depending on the context. Mastering this skill also builds the number sense you need for working with ratios, proportions, and probability.

Common Mistakes

Mistake: Forgetting to simplify the fraction after placing the percent over 100.
Correction: Always check whether the numerator and denominator share a common factor. For instance, 80/100 should be reduced to 4/5, not left as 80/100.
Mistake: Dividing by 10 instead of 100 when converting a percent to a fraction.
Correction: Remember that "percent" means per hundred, so the denominator must be 100. Writing 25% as 25/10 gives the wrong value; the correct fraction is 25/100 = 1/4.

Related Terms

  • FractionThe form you convert a percent into
  • DecimalIntermediate step when converting fractions to percents
  • NumeratorTop number that equals the percent when denominator is 100
  • DenominatorBottom number, set to 100 for percent conversion
  • Fraction RulesSimplifying rules used after conversion
  • Improper FractionResult when a percent exceeds 100
  • Mixed NumberAlternate form for percents over 100
  • RatioPercents and fractions both express ratios