Percentage

Percentage Calculator is a free, browser-based tool that handles every common percentage calculation in one place. A percentage is simply a fraction out of undefined - the word literally means "per hundred" - so 25% is the same as 25/100, or 0.25. That single idea powers a surprising amount of everyday maths: discounts, tips, tax, interest, test scores, growth rates and statistics all lean on it.

The tool covers the three questions people ask most: what is X% of a number (for example, undefined% of undefined), what percent is one number of another (for example, undefined out of undefined), and the percentage increase or decrease between two values (for example, from undefined to undefined). You type the numbers, the answer appears immediately, and the whole calculation runs on this page - nothing you enter ever leaves your device.

You can do percentages with a phone calculator, but the friction is in remembering which numbers to multiply or divide, and where the decimal point goes. It is easy to compute 55 / 40 when you meant (55 - 40) / 40, and get a confidently wrong answer. A dedicated tool labels each field so you put the right value in the right place and get the right formula applied for you.

It is also faster for the awkward cases - reversing a discount to find the original price, or working out percent change with a negative result - that trip people up on a basic calculator. Because Dev Nexus runs entirely in your browser, there is no sign-up, no waiting on a server, and nothing is logged. You can crunch salary figures, invoice totals or private numbers with confidence, and it keeps working when you are offline.

The three core calculations each come from one short formula:

• X% of a number: multiply the number by the percent as a decimal. undefined% of undefined is 80 × 0.15 = 12.
• What percent is A of B: divide A by B, then multiply by undefined. undefined out of undefined is 30 / 120 × 100 = 25%.
• Percentage change from A to B: subtract, divide by the original, then multiply by undefined. From undefined to undefined is (55 − 40) / 40 × 100 = 37.5% increase.

With the calculator you never touch the arithmetic. Pick the calculation, type the two numbers, and read the result. It handles decimals, rounds sensibly for display, and shows increases and decreases with the correct sign so you can tell growth from shrinkage at a glance.

Percentages show up everywhere, and a quick calculator saves time on all of them:

• Shopping and discounts: find the sale price after "undefined% off", or work backwards from a discounted price to the original.
• Tips and bills: add a undefined% or undefined% gratuity, then split it - for a dedicated flow, use the Tip Calculator.
• Finance: interest rates, tax, and simple growth. When the numbers become monthly loan payments, switch to the Loan / EMI Calculator.
• Grades and scores: turn "undefined out of undefined" into a percentage to see where a mark lands.
• Analytics and reporting: compute month-over-month growth or the percent change in any metric.
• Cooking and DIY: scale a recipe or a mix up or down by a percentage.

A few habits keep percentage maths accurate:

• Mind the base. Percent change is always relative to the original value, not the new one. A rise from undefined to undefined is a undefined.undefined% increase, but the drop from undefined back to undefined is only a undefined.undefined% decrease - different bases, different answers.
• A rise then an equal-percent fall does not return you home. Go up undefined% then down undefined% and you end up at undefined% of where you started, because the second percent is taken from a bigger number.
• Percentage points are not percentages. Moving from undefined% to undefined% is a rise of undefined percentage points, but a undefined% increase. Say which one you mean.
• Reverse discounts carefully. To undo a undefined% discount, divide the sale price by undefined.undefined, not multiply by undefined.undefined.
• Watch rounding. Round only at the final step; rounding partway through can push a result off by a whole percent.