Percentage Calculator
Work out a percentage of any amount, and increase or decrease it.
Your numbers
15% of 200
- 15% of 200
- 30
- Increased by 15%
- 230
- Decreased by 15%
- 170
Percentages are everywhere — discounts, tips, tax, interest, statistics — and the math is simpler than it feels once you know the few core formulas. Here's how to handle the most common percentage calculations without second-guessing yourself.
What "percent" means
"Percent" means "per hundred." So 15% is just 15 per 100, or the fraction 15/100 = 0.15. Converting a percentage to a decimal (divide by 100) is the key that unlocks every calculation.
Finding a percentage of a number
The most common task — what is X% of a value:
result = value × (percent ÷ 100)
What is 15% of 200? 200 × 0.15 = 30. The Percentage Calculator does this instantly and also shows the value increased and decreased by that percentage.
Percentage increase and decrease
To increase a value by a percentage, add the percentage amount; to decrease, subtract it:
- Increase 200 by 15%:
200 + 30 = 230 - Decrease 200 by 15%:
200 − 30 = 170
This is exactly how discounts ("15% off") and markups work.
Working out what percentage one number is of another
Sometimes you have the parts and want the percentage:
percent = (part ÷ whole) × 100
If 30 of 200 questions were correct: 30 ÷ 200 × 100 = 15%.
Percentage change between two numbers
To find how much something grew or shrank:
change = ((new − old) ÷ old) × 100
From 200 to 230: (230 − 200) ÷ 200 × 100 = 15% increase.
Everyday uses
- Tips: 18% of a $50 bill = $9.
- Discounts: 25% off a $80 item = $20 off, paying $60.
- Sales tax: 8% on $100 = $8.
- Interest: 5% on $1,000 = $50 a year.
The bottom line
Turn the percentage into a decimal, then multiply for "percent of," add or subtract for increase and decrease, and divide for "what percent." Use the Percentage Calculator for instant answers on discounts, tips, tax, and any everyday percentage.
Frequently asked questions
How do I find a percentage of a number?
Multiply the number by the percentage as a decimal: value × (percent ÷ 100). For example, 15% of 200 is 200 × 0.15 = 30. The calculator also shows the value increased and decreased by that percentage.
How do I calculate a percentage increase?
Find the percentage of the value and add it: value + (value × percent ÷ 100). Increasing 200 by 15% gives 200 + 30 = 230. A decrease subtracts instead, giving 170.
How do I work out what percentage one number is of another?
Divide the part by the whole and multiply by 100: (part ÷ whole) × 100. If 30 out of 200 are correct, that’s 30 ÷ 200 × 100 = 15%.
How do I calculate percentage change?
Use (new − old) ÷ old × 100. Going from 200 to 230 is (230 − 200) ÷ 200 × 100 = 15% increase. A negative result means a decrease.
How do I calculate a discount?
A discount is a percentage decrease. For 25% off $80: the discount is $80 × 0.25 = $20, so you pay $80 − $20 = $60. Enter the percentage and price to see it instantly.
How do I calculate a tip?
A tip is a percentage of the bill. For an 18% tip on a $50 bill: $50 × 0.18 = $9. The total with tip would be $59. Use the increase result to see the total directly.
What does "percent" actually mean?
“Percent” means “per hundred.” So 15% is 15 per 100, or the fraction 15/100 = 0.15. Converting a percentage to a decimal by dividing by 100 is the key step in every percentage calculation.
Can a percentage be more than 100%?
Yes. Percentages over 100% just mean more than the whole. 150% of 80 is 80 × 1.5 = 120. This is common with growth, markups, and returns that exceed the original amount.