Percentage Calculator
Tips, discounts, test scores, markups — if it involves a percent sign, this penguin does the math so you can move on with your day.
How to use
- Pick a mode. Choose "X% of Y" for tips and discounts, "X is what % of Y" for scores and shares, or "% change from X to Y" for growth and price changes.
- Enter your two numbers. Type the X and Y values into the fields — decimals are fine.
- Read the answer. The result updates as you type, and shows the full equation so you can double-check the math.
- Copy it if you need it. Hit "Copy result" to grab the answer for a message, spreadsheet, or receipt.
Frequently asked questions
How do I calculate what percent one number is of another?
Divide the first number by the second, then multiply by 100. For example, 45 is what percent of 180? Divide 45 by 180 to get 0.25, then multiply by 100 to get 25%. The "X is what % of Y" mode above does exactly this — just enter 45 and 180.
How do I calculate a percentage increase or decrease?
Subtract the old value from the new value, divide by the old value, and multiply by 100. If a price rose from $40 to $50, that's (50 − 40) ÷ 40 × 100 = 25% increase. A positive result means growth; a negative result means a decrease. Use the "% change from X to Y" mode to get it instantly.
How do I calculate X percent of Y?
Convert the percentage to a decimal and multiply. To find 20% of 150, divide 20 by 100 to get 0.2, then multiply by 150 to get 30. This is the most common percent calculation — it's how discounts ("25% off"), tips, and sales tax all work.
What is the difference between percent change and percentage points?
They measure different things. If your test score went from 70% to 80%, the change in percentage points is simply 80 − 70 = 10 points, but the percent change is (80 − 70) ÷ 70 × 100 ≈ 14.3%. Percent change is relative to where you started; percentage points are just the raw gap.
Why does my percentage calculation show a negative number?
A negative percent change means the new value is smaller than the old one — it's a decrease, not an error. For example, going from $100 to $80 is a −20% change. If you're using the "% change from X to Y" mode, make sure the older value is X and the newer value is Y.
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