Percentage Calculator

A Percentage Calculator is a versatile math tool that handles every common percentage operation in one place. Instead of memorizing formulas or reaching for a spreadsheet, you simply enter your numbers and get an instant answer. This calculator offers four distinct modes: Basic mode answers 'What is Y% of X?' — useful for calculating tips, sales tax, or exam scores. Reverse mode answers 'X is what percent of Y?' — perfect for figuring out what fraction one number represents of another. Change mode calculates the percentage increase or decrease between two values, which is essential for comparing prices, tracking stock performance, or measuring growth metrics. Finally, Discount/Markup mode applies a percentage to a base number, instantly showing you the final price after a discount or the total cost after a markup. All calculations happen in real time right in your browser, so there is no waiting and no data sent to any server. Whether you are a student solving homework problems, a shopper comparing deals, a business analyst reviewing quarterly figures, or anyone who works with numbers, this tool eliminates the guesswork from percentage math.

All four calculation sections are visible on the page simultaneously — no tabs or hidden panels. For Basic mode, enter the base number (X) and the percentage (Y), and the result appears instantly. For Reverse mode, enter the part value and the whole value to find what percentage the part represents. For Change mode, enter the original value and the new value to see the percentage increase or decrease. For Discount/Markup mode, enter the original price and the percentage, then choose whether to apply it as a discount or a markup. Each section shows its result in large text so you can read it at a glance.

Basic percentage uses the formula: result = X × Y / 100. Reverse percentage divides the part by the whole and multiplies by 100: result = (X / Y) × 100. Percentage change calculates the difference between two values relative to the original: result = ((New − Old) / |Old|) × 100. Discount mode multiplies by (1 − Y/100) while markup mode multiplies by (1 + Y/100). All arithmetic is performed using JavaScript's native floating-point numbers, and results are formatted to up to six decimal places with trailing zeros removed for clarity.