20% of 100 is:
20
20% = 0.2
0.2 × 100
20% of 100 = 20
Convert 20% to decimal (0.2) and multiply by 100
Calculate (20 ÷ 100) × 100 = 20
If a product costs $100 and has a 20% discount, you save $20
Scoring 20 out of 100 points gives you 20%
A 20% tip on a $100 bill is $20
(Percentage ÷ 100) × Number = Result
(20 ÷ 100) × 100 = 20
Understanding how to calculate percentages is an essential life skill that you'll use constantly in everyday situations. From calculating discounts while shopping to understanding test scores, tips at restaurants, tax rates, and investment returns - percentages are everywhere.
Calculate discounts, sales tax, tips, interest rates, and compare prices to make smart financial decisions.
Understand test scores, grade calculations, attendance rates, and academic performance metrics.
Interpret survey results, population data, growth rates, and statistical information in news and research.
Calculate nutritional information, body composition, workout intensity, and health metrics.
The word "percent" comes from the Latin "per centum," meaning "by the hundred." A percentage is simply a way of expressing a number as a fraction of 100. When we say 20%, we mean 20 parts out of every 100 parts.
The concept of percentages has been used for centuries because base-100 calculations are intuitive for humans (likely because we have 10 fingers, making base-10 and base-100 systems natural). Ancient Romans used fractions with denominators of 100, and by the 15th century, the % symbol emerged in Italian manuscripts.
There are three main types of percentage problems:
Mastering these three types of percentage problems will help you handle virtually any percentage calculation you encounter in daily life, academics, or professional work.
Moving the decimal point incorrectly
When converting 20% to a decimal, divide by 100 (move decimal 2 places left). 20% = 0.2000. Many students move it only one place.
Confusing percentage increase/decrease with the percentage of
"A 20% increase" means adding 20% to the original. "What is 20% of something" is just 20% × that number.
Forgetting that percentages over 100 are valid
You can have percentages greater than 100%. 200% of 50 = 100. This represents more than the whole, which is common when discussing growth or multiples.
Not checking if the answer makes sense
If 20% is less than 50%, your answer should be less than half of 100. If more than 50%, it should be more than half. Quick checks prevent big errors.
Memorize that 10% is ÷10, 25% is ÷4, 50% is ÷2, and 1% is ÷100. These benchmarks make mental math easier.
20% of 100 equals 100% of 20. Sometimes one calculation is easier! Try both ways.
Calculate 15% as 10% + 5%. Calculate 35% as 25% + 10%. Breaking down makes calculations manageable.
25% = ¼, 20% = ⅕, 50% = ½. Sometimes fraction multiplication is easier than decimal multiplication.
Before calculating 20% of 100, estimate: Is 20% close to 10%, 25%, 50%? This helps verify your final answer.
Calculate discounts while shopping. Figure out tips mentally at restaurants. Real practice builds lasting skills.
Multiply 100 by 20/100 (or 0.2000). The calculation is: 100 × 0.2000 = 20. You can also use the fraction method: 100 × 20/100.
The formula is: (Percentage ÷ 100) × Number = Result. Or equivalently: Number × (Percentage/100) = Result. For this problem: 100 × (20/100) = 20.
To convert any percentage to a decimal, divide by 100 (or move the decimal point two places to the left). 20% = 20 ÷ 100 = 0.2000.
20% as a fraction is 20/100. This can potentially be simplified depending on the numbers. The fraction represents 20 parts out of 100 equal parts.
Use estimation: If the percentage is less than 50%, your answer should be less than half the original number. If it's 100%, your answer equals the original. For 20% of 100, since 20% is less than half, 20 should be less than 50.
Percentages are used in calculating discounts (e.g., 20% off sale), tips at restaurants, tax calculations, interest rates on loans and savings, test scores and grades, nutritional information on food labels, statistical data, and business metrics like profit margins and growth rates.
To become confident with percentages, practice these types of problems: