📊 Percentage Calculator
Four percentage calculators in one: X% of Y, percentage change, X is what % of Y, and add/remove percentages. Instant results with step-by-step formulas — free, no login.
The Four Percentage Formulas You Need
Percentages underpin almost every quantitative analysis in business, science, and daily life — from calculating discounts and tax rates to measuring growth rates and statistical distributions. Understanding the four fundamental percentage formulas eliminates the need to memorize conversion factors and makes quick mental estimation possible.
| Calculation | Formula | Example |
|---|---|---|
| X% of Y | Y × (X / 100) | 15% of 200 = 30 |
| Percentage change | ((New−Old) / Old) × 100 | 80→100 = +25% |
| X is what % of Y | (X / Y) × 100 | 30/120 = 25% |
| Add/remove % | Y × (1 ± X/100) | 200 + 15% = 230 |
Percentage vs Percentage Points — A Critical Distinction
One of the most common quantitative errors in professional communication is confusing percentage increase with percentage points. If interest rates rise from 2% to 3%, that is a 1 percentage point increase — but a 50% increase in the rate itself. If an election polling share rises from 40% to 50%, that is a 10 percentage point increase but a 25% relative increase. Misusing these terms in financial analysis, journalism, or research papers leads to systematically misleading conclusions.
Frequently Asked Questions
How do I calculate percentage change?
Formula: ((New Value − Old Value) / Old Value) × 100. Example: price rises from $80 to $100 → ((100−80)/80) × 100 = 25% increase. Price drops from $100 to $80 → ((80−100)/100) × 100 = −20% decrease. Positive result = increase; negative = decrease.
What is the difference between percentage increase and percentage points?
Percentage points are an absolute difference between two percentages (2% to 3% = 1 percentage point). Percentage increase is a relative change (2% to 3% = 50% increase in rate). This distinction matters enormously in finance, economics, and statistics — always clarify which measurement is being used when reading or writing reports.
How do I calculate a discount percentage?
Discount % = ((Original − Sale) / Original) × 100. Example: $120 item on sale for $90 → ((120−90)/120) × 100 = 25% discount. Final price after discount: Original × (1 − Discount%/100) → 120 × 0.75 = $90.