Percentage Calculator
Calculate percentages, increases, decreases and ratios
Percentage Calculator covers the three percentage questions people actually need: what is X% of a number, what's the percentage increase or decrease between two values, and what percentage one number is of another — each with its own clear formula so the result is easy to check by hand.
How to use Percentage Calculator
- 1
Choose the calculation you need: "X% of Y", percentage change, or "what % is X of Y".
- 2
Enter the two numbers it asks for.
- 3
Click "Calculate" to see the result instantly.
- 4
Switch calculation types any time without re-entering your numbers from scratch.
Everything you need to know about percentage calculations
The three percentage questions people actually ask
- What is X% of Y? — e.g., what's 15% of $80.
- X is what percent of Y? — e.g., 12 out of 80 is what percent.
- Percentage increase/decrease — e.g., a price that went from $80 to $92, what's the percent change.
Why this comes up so often
Discounts, tips, tax, growth rates, and grade calculations all reduce to one of the three questions above — having a quick calculator for all three avoids re-deriving the formula each time.
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Frequently Asked Questions
What's the difference between the three calculation types?
"X% of Y" answers questions like a tip or discount amount. "Percentage change" answers how much a value grew or shrank, always measured against the starting value. "What percent is X of Y" answers questions like a test score or budget share.
Why isn't a 25% increase undone by a 25% decrease?
Because each percentage is calculated against a different base — the starting value changes after the first calculation, so the two percentages aren't symmetrical. See our full guide to percentage formulas for worked examples.
Can I calculate a percentage decrease, not just an increase?
Yes — the percentage change calculation returns a negative result automatically when the second value is lower than the first.
Does this tool send my numbers to a server?
Yes — the numbers are sent to our servers to compute the result and the result is returned to you; nothing is stored.
Is this tool free to use?
Yes — completely free, with no signup and no usage limits for casual use.