Percentage Calculator — Free, Instant, No Upload
Find X% of Y, add or subtract a percentage from a value, or calculate percentage change between two numbers. Instant results, no upload. Runs entirely in your browser.
How to use this tool
- Select the calculation type (e.g. "X% of Y" or "what % is X of Y").
- Enter the values.
- Read the instant result.
About Percentage Calculator
Percentages express a number as a fraction of one hundred, and most everyday percentage questions fall into a few distinct shapes. This calculator covers four of them. Find X% of Y multiplies the two together: X% of Y = (X / 100) × Y, so 15% of 80 is (15/100) × 80 = 12. Add a percentage scales a value up by that proportion: Y + X% = Y × (1 + X/100), so 80 increased by 15% is 92. Subtract a percentage scales it down: Y − X% = Y × (1 − X/100), so 80 reduced by 15% is 68. Percentage change compares an old value to a new one: ((New − Old) / Old) × 100, so going from 80 to 92 is a 15% increase.
These map onto common real-world tasks. Find X% of Y handles a tip, a commission, or a sales-tax amount. Add a percentage gives a price after tax or a markup, while subtract a percentage gives a sale price after a discount or a figure net of a deduction. Percentage change is the right tool for measuring growth or decline between two points — a price rise, a drop in expenses, or a change in a metric over time. Choosing the correct mode is the key step; the same two numbers can give very different answers depending on which relationship you mean.
A few subtleties trip people up. Adding then removing the same percentage does not return the original number: 100 increased by 10% is 110, but 110 reduced by 10% is 99, because the 10% is taken from a larger base the second time. Likewise a 50% fall followed by a 50% rise leaves you below where you started. Percentage change is also directional and is always measured relative to the starting value, so a rise from 80 to 100 (+25%) is not the mirror of a fall from 100 to 80 (−20%). And percentage points are not percentages: a rate moving from 4% to 6% is a 2 percentage-point rise but a 50% relative increase.
The calculator gives exact arithmetic for whatever values you enter, with no rounding beyond what is displayed. It is purely a math helper, so the interpretation is up to you — make sure the "old" and "new" values are the right way round for a change calculation, and that the base you are taking a percentage of is the one you intend. Everything runs in your browser with nothing sent to a server.
Frequently Asked Questions
- What calculations can this tool do?
- Four common percentage operations: find X% of a value, add a percentage to a value, subtract a percentage from a value, and calculate the percentage change between two values. Pick the mode that matches your question, enter the numbers, and the result updates instantly.
- How do I find X% of a number?
- Use the "X% of Y" mode, which computes (X / 100) × Y. For example, 15% of 80 is (15/100) × 80 = 12. This is the operation behind tips, commissions, and working out a tax or interest amount from a rate.
- How is percentage change calculated?
- Using ((New − Old) / Old) × 100. The change is always measured relative to the old (starting) value. A positive result is an increase and a negative result is a decrease, so going from 80 to 100 is a +25% change and from 100 to 80 is a −20% change.
- Why don't adding and then subtracting the same percentage cancel out?
- Because each percentage is taken from a different base. Increasing 100 by 10% gives 110, but reducing 110 by 10% removes 11 (10% of 110), leaving 99. The second percentage is applied to a larger number, so the two operations do not undo each other.
- What is the difference between a percentage and a percentage point?
- A percentage point is the arithmetic gap between two percentages, while a percent change is relative. A rate moving from 4% to 6% rises by 2 percentage points, but that is a 50% relative increase. Confusing the two is a common source of misleading statistics.
- How do I work out a discount or a price after tax?
- For a discount, use subtract mode: a price of 80 less 15% becomes 80 × (1 − 0.15) = 68. For a price including tax, use add mode: 80 plus 15% becomes 80 × (1 + 0.15) = 92. The "X% of Y" mode gives just the discount or tax amount on its own.
- Is my data sent anywhere?
- No. All calculations run locally in your browser. The numbers you enter are never uploaded, stored, or shared, and no account is required to use the tool.
Embed this tool on your site
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<iframe src="https://brevio.pro/embed/percentage-calculator" width="100%" height="600" loading="lazy" style="border:1px solid #e5e5e5;border-radius:8px" title="Percentage Calculator — brevio"></iframe> <p style="font:12px/1.4 sans-serif"><a href="https://brevio.pro/tools/percentage-calculator">Percentage Calculator</a> by <a href="https://brevio.pro">brevio</a></p>