Percentage Calculator
Find what P% of any number is — instant answers with the formula shown.
Formula
To find P percent of a value X, convert the percentage to a decimal and multiply: result = X × (P ÷ 100). For example, 20% of 150 = 150 × 0.20 = 30.
Worked example
What is 15% of 200? Multiply 200 × (15 ÷ 100) = 200 × 0.15 = 30. So 15% of 200 is 30.
How to use the percentage calculator
This calculator answers one question: what is P% of X? It does not calculate percent increase, percent decrease or percent change. The next section shows how those differ.
- Enter the percentage. Type it as a plain number, such as 20 for 20%.
- Enter the value. This is the number you want to take the percentage of, such as 150.
- Read the result. The calculator shows the answer along with the formula it used.
Worked example
A jacket costs $150 and the sale is 20% off. To find the discount amount, enter 20 as the percentage and 150 as the value.
The formula is result = X × (P ÷ 100), so 150 × (20 ÷ 100) = 150 × 0.20 = 30. The discount is $30, which makes the sale price $120.
Percentage formulas you'll actually use
Percentage questions sound alike but use different formulas. Only the first one is what this calculator does. For the other three, you'll need to work them out yourself or use a different tool.
P% of X (what this calculator does)
Formula: X × (P ÷ 100)
Example: 35% of 240 = 240 × 0.35 = 84.
What percent is X of Y?
Formula: (X ÷ Y) × 100
Example: 18 out of 72 is (18 ÷ 72) × 100 = 25%.
Percent increase
Formula: ((new − old) ÷ old) × 100
Example: Going from 50 to 65 is (15 ÷ 50) × 100 = 30% increase.
Percent decrease
Formula: ((old − new) ÷ old) × 100
Example: Going from 80 to 60 is (20 ÷ 80) × 100 = 25% decrease.
A mental-math shortcut
a% of b is always the same as b% of a. If 18% of 50 feels awkward, flip it: 50% of 18 is just half of 18, which is 9. Both give 9. For background on how percentages work, see the Wikipedia article on percentages.
Where percentages show up in real life
Discounts and sales
A $64 pair of shoes is 25% off. 25% of 64 is $16, so you pay $48.
Tips
Your meal comes to $45 and you want to leave 18%. 18% of 45 is $8.10, so the tip is $8.10 and the total is $53.10.
Tax and VAT
Sales tax of 8% on a $120 purchase adds 8% of 120, which is $9.60, for a total of $129.60. VAT works the same way: 20% of £50 is £10 added to the price.
Exam grades and commissions
If an exam is worth 30% of your final grade and you scored 80, it contributes 30% of 80 = 24 points. Commissions follow the same pattern: 5% of $2,000 in sales is $100.
Percentages also matter when you borrow or save. To see how a rate plays out over time, try the loan EMI calculator or the compound interest calculator.
Common percentage mistakes
- Confusing "percent of" with "percent increase." 20% of 150 is 30, but a 20% increase on 150 is 150 + 30 = 180.
- Forgetting to divide by 100. Multiplying 150 by 20 gives 3,000, but 20% means 20 ÷ 100 = 0.20, so the answer is 30.
- Using the wrong starting value for change. Going from 50 to 65 is a 30% increase, but going from 65 back to 50 is only about a 23.1% decrease, because the base is now 65.
Frequently asked questions
How do I calculate a percentage of a number?
Divide the percentage by 100, then multiply by the number. For 20% of 150, that is 150 × 0.20 = 30. The calculator does this when you enter the percentage and the value.
What's the difference between “percent of” and “percent increase”?
“Percent of” gives you a portion of a number. “Percent increase” tells you how much a number grew compared to where it started. 20% of 150 is 30, but increasing 150 by 20% gives 180. This calculator handles the first case only.
How do I find what percent one number is of another?
Divide the first number by the second and multiply by 100. For example, 18 is (18 ÷ 72) × 100 = 25% of 72. This is a different question from “what is P% of X,” so it needs a different formula.
Can a percentage be more than 100?
Yes. A percentage over 100 means more than the whole. 150% of 40 is 60, which is 40 plus another half of 40.
Why do you divide by 100 when calculating a percentage?
“Percent” means “per hundred,” so 20% is 20 out of 100, or 20 ÷ 100 = 0.20. Multiplying by that decimal gives the correct share of the number.
