--- title: "Percentage Calculator - Free Online Percent Tool | CanDoYa" description: "Free percentage calculator: find X% of a number, what percent one number is of another, and percent increase or decrease - instantly in your browser." url: https://candoya.com/tools/percentage-calculator/ locale: en type: browser-tool --- # Free Percentage Calculator Category: Calculators ## How do you calculate a percentage? To calculate a percentage, divide the part by the whole and multiply by 100: (part ÷ whole) × 100. This free percentage calculator solves the three everyday percent problems live - what is X% of a number, what percent one number is of another, and the percentage increase or decrease between two values. Everything runs **locally in your browser**. Your numbers are never uploaded or stored, results update on every keystroke, and each answer shows the worked formula with your values substituted in - so you can check the math or reuse it by hand. It works offline once the page has loaded. ## How to use it 1. **Pick the row that matches your question** - The calculator shows three fill-in-the-blank sentences: percentage of a number, what percent one number is of another, and percentage change from one value to another. 2. **Type your two numbers** - Fill both blanks in that sentence. Decimals (dot or comma) and negative numbers work, and the result updates as you type. 3. **Read and copy the result** - The answer appears next to the sentence with the worked formula underneath. Percentage change is labeled as an increase or a decrease. Use Copy to grab the value. ## Who it's for - **Shoppers** working out a 25% discount, a tip, or how much a price actually rose after two increases. - **Students** converting test marks into percentages and checking percentage-change homework against the worked formula. - **Small-business owners** figuring margins, VAT or sales tax amounts, and month-over-month revenue change. - **Investors and savers** measuring how much a portfolio, price, or balance went up or down in percent terms. - **Anyone comparing numbers** - poll results, weight change, battery capacity - who wants the percent, not just the difference. ## Expert note Percentage change here divides by the absolute starting value, (new − old) ÷ |old| × 100, so a change from a negative start (say −40 to 10) still reads correctly as an increase; and note the asymmetry trap: a 50% drop needs a +100% rise to get back to where you started. ## Frequently asked questions ### Is this percentage calculator free? Yes - 100% free, no sign-up, and no limits. All three calculators run entirely in your browser, so they also work offline once the page has loaded. ### Are my numbers uploaded anywhere? No. The math happens locally on your device with plain JavaScript. Nothing you type is sent to a server, stored, or shared - close the tab and it is gone. ### How do I calculate the percentage of a number? Multiply the number by the percent and divide by 100: P% of X = P × X ÷ 100. For example, 25% of 80 is 25 × 80 ÷ 100 = 20. The first row of the calculator does exactly this and shows the substitution. ### How do I work out what percent one number is of another? Divide the part by the whole and multiply by 100: (part ÷ whole) × 100. For example, 30 of 150 is 30 ÷ 150 × 100 = 20%. If the whole is 0 the answer is undefined - you cannot divide by zero. ### How is percentage increase or decrease calculated? Take the difference, divide by the absolute starting value, and multiply by 100: (new − old) ÷ |old| × 100. Going from 40 to 50 is (50 − 40) ÷ 40 × 100 = +25%, an increase; from 50 to 40 is −20%, a decrease. ### What is the difference between percent change and percentage points? Percent change is relative to the starting value; percentage points are the plain difference between two percentages. If a rate moves from 10% to 15%, that is a rise of 5 percentage points but a 50% increase - saying which one you mean avoids a very common misreading. ### Why doesn't a 50% decrease cancel a 50% increase? Because each step is measured against a different base. 100 up 50% is 150, but 150 down 50% is 75, not 100. The smaller the base, the bigger the percent a fixed change represents - that is why a 50% loss needs a 100% gain to recover. ## Related tools - [Z-Score Calculator](https://candoya.com/tools/z-score-calculator/) - [Perimeter Calculator](https://candoya.com/tools/perimeter-calculator/) - [Integral Calculator](https://candoya.com/tools/integral-calculator/) - [Correlation Coefficient Calculator](https://candoya.com/tools/correlation-coefficient/) - [Standard Deviation Calculator](https://candoya.com/tools/standard-deviation-calculator/) --- *Markdown edition of , published for AI agents and other automated readers. Index of key pages: .*