Percentage Calculator
Calculate any percentage: find what percent one number is of another, calculate percent increase or decrease, or find X% of any number — with the formula shown.
How this calculator works
This calculator covers the three most common percentage questions at once: what percent X is of Y, what X% of Y equals, and the percentage change between X and Y. If you only need quick everyday arithmetic without percentages, the Basic Calculator covers the four core operations.
X = part or first value · Y = whole or second value
Common percentage calculations
"What percent is X of Y" divides X by Y and multiplies by 100. "What is X% of Y" multiplies Y by X divided by 100. Percentage change compares two values relative to the original, and is one of the most commonly misunderstood calculations in everyday math. For a fuller walkthrough with more worked examples, see our complete guide to calculating percentages.
These three calculations cover the vast majority of real-world percentage questions — from figuring out a tip or discount, to understanding a test score, to tracking how much a price or metric has grown or shrunk over time.
Worked examples
Example 1 — What percent is X of Y: If you scored 42 out of 50 on a test, that's (42 ÷ 50) × 100 = 84%. This is the calculation behind grades, survey results, and completion rates.
Example 2 — What is X% of Y: A store advertises 25% off a $80 jacket. That's (25 ÷ 100) × 80 = $20 off, making the sale price $60. This is the calculation behind discounts, tips, and taxes.
Example 3 — Percentage change: A stock priced at $40 rises to $52. The percentage change is ((52 − 40) ÷ 40) × 100 = 30% increase. If it had instead fallen to $32, the change would be ((32 − 40) ÷ 40) × 100 = −20%, a 20% decrease.
Percent vs. percentage points — a common mix-up
One of the most frequent errors in percentage math is confusing a percentage change with a percentage point change. If an interest rate moves from 5% to 7%, that's a 2 percentage point increase — but expressed as a relative percentage change, it's a 40% increase (2 ÷ 5 × 100), since it's measured relative to the starting value.
This distinction matters in finance, statistics, and news reporting, where a headline like 'unemployment rose by 2%' could mean either a 2 percentage point rise (e.g., 4% to 6%) or a 2% relative increase (e.g., 4% to 4.08%) — two very different outcomes.
Percentages in everyday situations
Restaurant tipping: an 18% tip on a $64 bill is (18 ÷ 100) × 64 = $11.52, bringing the total to $75.52. Most people round to the nearest dollar for simplicity, which is close enough for practical purposes. Use the Tip Calculator for quick tip amounts.
Sales tax: at an 8% rate, a $45 item costs an additional (8 ÷ 100) × 45 = $3.60 in tax, for a total of $48.60. Combined discount-then-tax calculations (like a discounted item that's then taxed) should always apply the discount first, then calculate tax on the reduced price. See also the Sales Tax Calculator and Discount Calculator.
Grade curves and scores: if a class average was 68% and a professor adds a flat 7 percentage points to everyone's grade, a student who scored 75% would move to 82% — a straightforward percentage point addition, not a percentage increase, which is a common point of confusion for students checking their curved grades.
Frequently asked questions
How do you calculate a percentage increase?
Subtract the original value from the new value, divide by the original value, then multiply by 100. A positive result is an increase; a negative result is a decrease.
What is the difference between percent and percentage points?
A percentage is a relative measure (e.g. a 50% increase), while a percentage point is an absolute difference between two percentages (e.g. going from 40% to 45% is a 5 percentage point increase, or a 12.5% relative increase).
How do I calculate a percentage without a calculator?
For simple percentages, convert to a fraction first — 25% is 1/4, 50% is 1/2, 10% is 1/10 — then apply that fraction to the number. For 10%, just move the decimal point one place left.
Why does my percentage calculation give a different answer than expected?
The most common cause is mixing up which value is the 'whole' (denominator) — make sure you're dividing the part by the correct original or total value, not the other way around.
How is percentage used in everyday finance?
Interest rates, discounts, sales tax, tips, and investment returns are all expressed as percentages, making this one of the most practically useful calculations in daily life.
How do I calculate a percentage of a number?
Multiply the number by the percentage and divide by 100. Formula: result = (number × percentage) / 100. Example: 20% of 150 = (150 × 20) / 100 = 30. Or simply multiply by the decimal: 150 × 0.20 = 30.
How do I calculate what percentage one number is of another?
Divide the part by the whole and multiply by 100. Formula: percentage = (part / whole) × 100. Example: 45 out of 180 = (45/180) × 100 = 25%. This tells you that 45 is 25% of 180.
How do I calculate percentage increase or decrease?
Percentage change = ((new value - old value) / old value) × 100. If the result is positive, it is an increase. If negative, it is a decrease. Example: price rose from $50 to $65 — change = ((65-50)/50) × 100 = 30% increase.
What is 20% of 100?
20% of 100 is 20. Formula: 100 × 0.20 = 20. This is a common percentage calculation used for tips, discounts, and tax estimates.
How do I find what percentage one number is of another?
Divide the part by the whole and multiply by 100. Example: what percentage is 45 of 200? = (45 ÷ 200) × 100 = 22.5%. So 45 is 22.5% of 200.