Percentage Calculator

Percentages appear in nearly every domain of daily life — from calculating a restaurant tip to understanding how much a stock gained, finding a test score, comparing year-over-year business growth, or reading a nutrition label's daily-value column. This percentage calculator covers the three operations people encounter most often and delivers precise results without any algebra. The first mode, finding X% of Y, is the most commonly used percentage calculation. It powers discount amounts, sales tax estimates, tip computations, commission calculations, and nutritional daily-value readings. The second mode, finding what percent X is of Y, converts raw comparisons into intuitive ratios instantly. A student who scored 54 out of 75 wants the percentage without opening a spreadsheet; a project manager tracking 28 of 140 completed tasks wants the progress percentage at a glance. The third mode, percentage change, is especially valuable in financial and scientific contexts. Investors use it to measure portfolio returns; businesses use it in quarterly earnings reports; researchers use it to express experimental results relative to a baseline control. The formula correctly handles both increases and decreases and labels the direction alongside the magnitude. All three modes use exact arithmetic without intermediate rounding, so results are reliable for use in homework, financial models, and professional presentations.

This calculator handles three distinct percentage operations, each using its own formula. Mode 1 — 'What is X% of Y?': Result = (X ÷ 100) × Y. This finds a fractional portion of a number. For example, 15% of 200 = (15 ÷ 100) × 200 = 0.15 × 200 = 30. Use this for tips, tax amounts, discounts, and commission figures. Mode 2 — 'X is what % of Y?': Result = (X ÷ Y) × 100. This expresses X as a proportion of Y scaled to a 0–100 range. For example, 45 is what % of 180 = (45 ÷ 180) × 100 = 25%. Use this for test scores, completion rates, and market share calculations. Mode 3 — 'Percentage change from X to Y': Result = ((Y − X) ÷ |X|) × 100. This measures the relative change between a starting and ending value. The formula uses the absolute value of X in the denominator so it behaves correctly even when the starting value is negative. A positive result is an increase; a negative result is a decrease. For example, from 80 to 100: ((100 − 80) ÷ 80) × 100 = 25% increase. The absolute difference between X and Y is displayed alongside the percentage so you have both the relative and absolute context.