Percentage Calculator — Find %, Increase, Decrease & Ratio
Calculate percentages four ways: find X% of Y, compute percentage increase or decrease, and determine what percentage one number is of another. Instant results with clear formulas for every mode.
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"Percent" literally means "per hundred" — from the Latin "per centum" A 50% increase followed by a 50% decrease does NOT return to the original value (it yields 75%) Percentage points and percentages are different: going from 10% to 15% is a 5 percentage point increase but a 50% increase To reverse a percentage increase of X%, decrease by X/(100+X) × 100%
Ready to run the numbers?
Why: Percentages are the universal language of comparison. Sales tax, interest rates, exam scores, election polls, medical statistics, stock returns, tip calculations, nutrition labels — percentages are everywhere. Understanding them is critical for financial literacy, data analysis, and informed decision-making in daily life.
How: Choose one of four calculation modes: (1) What is X% of Y? (2) What is Y increased by X%? (3) What is Y decreased by X%? (4) What percentage is X of Y? Enter your values and get instant results. Each mode uses a clear formula: basic percentage = value × (percent/100), increase = original × (1 + percent/100), etc.
Run the calculator when you are ready.
Basic Percentage
Calculate a percentage of a number
How to Use This Calculator
Basic Percentage: Enter a value and the percentage you want to calculate. The calculator will show you what percentage of the value is.
Percentage Increase: Enter an original value and a percentage increase. The calculator will show you the new value after the increase has been applied.
Percentage Decrease: Enter an original value and a percentage decrease. The calculator will show you the new value after the decrease has been applied.
What Percentage is X of Y: Enter a part value (X) and a whole value (Y). The calculator will tell you what percentage X is of Y.
Common Percentage Applications
Sales and Discounts
Calculate discounted prices during sales, or determine the percentage savings on a purchase.
Tips and Gratuities
Quickly calculate appropriate tip amounts when dining out or using services.
Financial Planning
Calculate interest rates, investment growth, or budget percentages for savings and expenses.
Academic Grading
Convert raw scores to percentages, or determine what percentage of a total grade an assignment contributes.
For educational and informational purposes only. Verify with a qualified professional.
🧮 Fascinating Math Facts
The % symbol evolved from the Italian "per cento." By the 17th century, scribes shortened it to "p cento," then "p 100," then "p/o," and finally the modern % sign.
— Oxford English Dictionary
Compound interest at 7% doubles your money in about 10 years (the Rule of 72: divide 72 by the interest rate to estimate doubling time).
— Investopedia
Research shows that expressing risks as frequencies (1 in 100) is better understood than percentages (1%) — yet percentages dominate media reporting.
— BMJ, Gigerenzer 2003
A price marked "50% off, then additional 20% off" is NOT 70% off — it's actually 60% off the original price (0.5 × 0.8 = 0.4, so 40% of original).
— Math is Fun
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