Free online percentage calculator: find X% of Y, what percent X is of Y, and compute percentage increases or decreases — with instant results.
Enter values to see calculation explanation.
Choose the calculation type you need from the dropdown — options include 'X% of Y', 'X is what % of Y', 'percentage change', 'increase by %', 'decrease by %', and 'reverse percent'.
Enter your numbers in the input fields. The tool validates entries in real time and highlights any invalid inputs.
Read the calculated result and the step-by-step formula displayed below it. The formula shows every operation so you can replicate it by hand.
Optionally copy the result to your clipboard or clear the fields to start a new calculation.
Handles the six most common percentage problems in a single interface — basic percent of a number, reverse percent, percent difference, percent change, increase by a percent, and decrease by a percent. No need to switch between multiple tools.
Results update instantly as you type, and the full algebraic formula is displayed beneath each answer so you can understand and verify the math yourself.
The tool gracefully handles zero denominators, negative values, and very large numbers, displaying a clear explanation instead of crashing or showing NaN.
Every calculation runs entirely inside your browser using JavaScript. No inputs are transmitted to any server, logged, or stored — your numbers stay on your device.
Tap targets are sized for thumb use on phones and tablets. The layout adjusts to any screen width without horizontal scrolling.
Unlike many online calculators that send your inputs to a backend for processing, this tool runs 100% client-side. Your salary figures, investment amounts, and tax rates never leave your browser. There is no account required and no data is ever collected.
Every result is accompanied by the full formula with your actual values substituted in. This means you learn the math behind the answer — useful for students, teachers, and anyone who wants to double-check results manually or explain them to others.
Most calculators only solve one or two types of percentage questions. This tool covers all six in one place — from 'what is 15% of $85?' to 'a price rose from $40 to $52, what was the percent increase?' — saving time and reducing context switching.
Results are computed using standard arithmetic with no rounding until display. The tool does not assume tax rates, discount schedules, or any external values — you supply all inputs, so the output is exactly as precise as your inputs.
A percentage is a dimensionless ratio expressed as a fraction of 100. The word comes from the Latin per centum, meaning "out of a hundred." Writing a number as a percentage is a way to make comparisons easier: saying a fund returned 7.2% is more intuitive than saying it returned 0.072 of its value.
Percentages underpin an enormous range of real-world calculations — income tax brackets, credit card interest rates, nutritional labels, grade point averages, clinical trial efficacy rates, and discount pricing all rely on percentage arithmetic. Mastering the underlying formulas lets you verify any of these figures independently.
1. Find X% of Y (basic percent of a number)
Formula: result = (X ÷ 100) × Y
Example: 18% of $250 = (18 ÷ 100) × 250 = $45.00
2. X is what percent of Y? (find the rate)
Formula: rate = (X ÷ Y) × 100
Example: $45 is what percent of $250? = (45 ÷ 250) × 100 = 18%
3. X is Y% of what? (reverse percent / find the whole)
Formula: whole = X ÷ (Y ÷ 100)
Example: $45 is 18% of what? = 45 ÷ 0.18 = $250.00
4. Percentage change (increase or decrease)
Formula: change% = ((new − old) ÷ |old|) × 100
Example: A stock rises from $80 to $92 → ((92 − 80) ÷ 80) × 100 = +15%
5. Increase a value by X%
Formula: result = original × (1 + X ÷ 100)
Example: $200 increased by 8% = 200 × 1.08 = $216.00
6. Decrease a value by X%
Formula: result = original × (1 − X ÷ 100)
Example: $200 decreased by 8% = 200 × 0.92 = $184.00
Personal Finance: Calculating a 20% tip on a $65 restaurant bill ($13.00), or determining what a 3.5% savings account APY earns on a $5,000 balance after one year ($175.00). Keep in mind that APY calculations for compound interest require additional steps beyond simple percentage arithmetic.
Shopping and Discounts: A $120 jacket marked 35% off costs $120 × (1 − 0.35) = $78.00 before tax. If your state adds 8.25% sales tax, the final price is $78.00 × 1.0825 ≈ $84.44. This tool handles each step separately; chain the operations yourself for multi-step scenarios.
Business and Investing: Gross margin percentage = ((revenue − cost) ÷ revenue) × 100. If a product sells for $50 and costs $32 to produce, the gross margin is ((50 − 32) ÷ 50) × 100 = 36%. Note that margin and markup are different figures — markup is calculated over cost, not revenue.
Academic Grading: A student scores 73 out of 85 points. Their percentage score = (73 ÷ 85) × 100 ≈ 85.9%. Always verify how your institution rounds final grades.
This calculator handles single-step percentage arithmetic. It does not calculate compound interest, loan amortization schedules, or multi-period growth rates — those require dedicated financial calculators. The results depend entirely on the numbers you enter; always verify inputs when working with financial data that affects decisions.
Subtract the original value from the new value to get the change. Then divide that change by the original value and multiply by 100. Formula: ((new − old) ÷ old) × 100. Example: if a price rises from $80 to $100, the increase is ((100 − 80) ÷ 80) × 100 = 25%.
Yes. Every calculation runs entirely inside your web browser using JavaScript. No numbers you enter are sent to any server, stored in a database, or logged in any way. You can verify this by opening your browser's developer tools and checking that no network requests are made when you type.
Yes. For a tip, use 'increase by X%' mode — enter the bill amount and the tip percentage. For sales tax, use the same mode with your local tax rate. Note that this tool calculates each step separately; if you need a total including both a discount and a tax, run two separate calculations.
This is the reverse percent problem. You know a portion and the rate, and you want to find the original whole. For example: '$45 is 18% of what amount?' The answer is 45 ÷ 0.18 = $250. This is useful when you know a discounted price and the discount rate and want to recover the original price.
A percentage point is the arithmetic difference between two percentages. If a pass rate rises from 60% to 75%, it increased by 15 percentage points. The percent change in that rate is ((75 − 60) ÷ 60) × 100 = 25%. These are different measures — journalists and marketers sometimes use them interchangeably, which creates confusion.
Use the formula: ((old − new) ÷ old) × 100. Example: a $120 item drops to $90 — the decrease is ((120 − 90) ÷ 120) × 100 = 25% off. Alternatively, use the 'decrease by X%' mode if you already know the percentage and want to find the resulting value.
Because the percentage is applied to different base values each time. Starting at $100: a 50% increase gives $150. A 50% decrease on $150 gives $75 — not $100. Percentage changes are multiplicative, not additive. This is why investment returns must be compounded rather than added.
Yes, completely free with no usage limits, no registration, no ads injected into results, and no premium tiers. All six calculation modes are available at no cost. Bookmark the page for quick access whenever you need fast, accurate percentage math without installing any software or app.