A percentage calculator online is one of the most frequently needed tools for everyday math. Whether you are figuring out a restaurant tip, calculating a discount during a sale, determining your grade on an exam, or analyzing financial data, percentages come up constantly. This free percentage calculator gives you four distinct calculation modes so you can solve any percentage problem in seconds without reaching for a formula or opening a spreadsheet.
All four calculators above run entirely in your browser. Enter your numbers, click a button, and the result appears instantly. There is nothing to install, no account to create, and no data leaves your device.
What Is a Percentage Calculator Online?
A percentage calculator online is a browser-based tool that performs common percentage computations for you. Instead of remembering formulas and doing the arithmetic by hand, you enter two numbers and the calculator does the rest. The word "percent" comes from the Latin per centum, meaning "by the hundred." When we say 25%, we mean 25 out of every 100, or equivalently, 0.25 as a decimal.
Percentage calculations appear in virtually every field. Retailers mark items up and discount them using percentages. Financial analysts track percentage changes in stock prices and revenue. Teachers convert raw scores to percentages to assign grades. Nutritionists express daily values as percentages. Even sports statistics like free-throw percentages and batting averages are rooted in the same math. Having an instant calculator removes the friction from all of these tasks.
This tool offers four modes because most percentage questions fall into one of four categories: finding a percentage of a value, figuring out what percent one number is of another, measuring the percentage change between two values, and adjusting a value up or down by a given percent. Each mode has its own section above with clearly labeled inputs, so you always know which formula is being applied.
How to Calculate Percentages
Understanding the formulas behind each mode will help you verify results and work through problems even when you do not have a calculator handy. Here are the four core percentage formulas this tool uses:
Formula 1: What is X% of Y?
This is the most common percentage calculation. The formula is:
Result = (X / 100) × Y
For example, 25% of 200 equals (25 / 100) × 200 = 50. You would use this to calculate a tip (what is 20% of $65?), find a discount amount (what is 30% of $89.99?), or determine tax (what is 8.25% of $42?).
Formula 2: X is what % of Y?
This formula tells you the ratio of one number to another, expressed as a percentage:
Percentage = (X / Y) × 100
For example, 50 is what percent of 200? The answer is (50 / 200) × 100 = 25%. This is useful for calculating grade percentages (you scored 42 out of 50 — that is 84%), market share, or how much of your budget a single expense represents.
Formula 3: Percentage change from X to Y
Percentage change measures how much a value increased or decreased relative to the starting point:
Percentage Change = ((Y - X) / |X|) × 100
Going from 80 to 100 is a 25% increase: ((100 - 80) / 80) × 100 = 25%. Going from 100 to 80 is a 20% decrease: ((80 - 100) / 100) × 100 = -20%. Notice that the percentage increase and decrease between the same two numbers are not equal because the base value differs.
Formula 4: Increase or decrease X by Y%
To increase a value by a percentage:
Result = X × (1 + Y / 100)
To decrease a value by a percentage:
Result = X × (1 - Y / 100)
For example, increasing 150 by 20% gives 150 × 1.20 = 180. Decreasing 150 by 20% gives 150 × 0.80 = 120. This is how retailers calculate sale prices and how employers compute raises.
Common Percentage Calculations Explained
Here are five real-world scenarios where percentage calculations come up most often, along with how to solve each one:
Tip Calculation
At a restaurant, you typically tip between 15% and 20% of the pre-tax bill. If your bill is $65 and you want to leave a 20% tip, use the first calculator: enter 20 as the percentage and 65 as the value. The result is $13. Your total becomes $78. For quick mental math, find 10% ($6.50) and double it.
Discount and Sale Price
When an item is marked 30% off, you need two steps: first calculate the discount amount, then subtract it from the original price. If a jacket costs $120 and is 30% off, the discount is (30 / 100) × 120 = $36, and the sale price is $120 - $36 = $84. Alternatively, use the fourth calculator and decrease $120 by 30% to get $84 directly.
Sales Tax
Sales tax works like a percentage increase. If your state has an 8.5% sales tax on a $50 purchase, use the fourth calculator and increase $50 by 8.5%. The result is $54.25. For more detailed tax scenarios with multiple rates and exemptions, our tax calculator online provides dedicated fields for federal and state rates.
Grade Percentage
To convert a raw score to a percentage, use the second calculator. If you scored 38 out of 45 on a test, enter 38 and 45. The result is 84.44%, which is typically a B grade. This method works for any scoring system — just divide the points earned by the total possible points.
Markup and Profit Margin
Businesses use percentage markup to set prices above cost. If a product costs $40 to make and you want a 60% markup, use the fourth calculator to increase $40 by 60%. The selling price is $64. Note that markup percentage and profit margin percentage are different: a 60% markup on $40 gives a $24 profit, but the profit margin is $24 / $64 = 37.5%.
Percentage vs Percentile — What's the Difference?
These two terms sound similar but mean very different things. A percentage is a ratio that expresses a number as a fraction of 100. When you say you scored 85% on a test, you mean you got 85 out of every 100 possible points.
A percentile, on the other hand, is a ranking relative to a group. If you scored in the 90th percentile on a standardized test, it means you performed better than 90% of all test takers. It does not mean you got 90% of the questions correct. You could score 72% on the test and still be in the 95th percentile if most other students scored below 72%.
Percentages measure a proportion. Percentiles measure a position in a distribution. This calculator handles percentages. For percentile calculations, you would need a dataset and a statistical tool that can sort values and determine rankings.
Understanding this distinction matters in contexts like SAT scores, income distribution, growth charts for children, and any scenario where relative standing is compared. A high percentage does not always mean a high percentile, and vice versa.
When to Use a Percentage Calculator
While percentage math is straightforward in concept, there are situations where a dedicated calculator saves meaningful time and reduces errors:
- Shopping and budgeting: Quickly compare discounts, calculate tips, or figure out how much tax adds to a purchase. Having the answer in seconds helps you make spending decisions on the spot.
- School and academics: Convert raw test scores to percentages, determine what score you need on a final exam to achieve a target grade, or calculate weighted averages across assignments.
- Business and finance: Track percentage changes in revenue, calculate profit margins, determine markup prices, or figure out year-over-year growth rates. For compound growth over time, our compound interest calculator online provides a visual growth chart and supports monthly contributions.
- Data analysis: When comparing datasets, percentage change is more meaningful than absolute change. A $10 increase on a $100 item (10%) is very different from a $10 increase on a $1,000 item (1%), even though the dollar amount is the same.
- Health and fitness: Calculate body fat percentage changes, determine what percentage of daily caloric intake a meal represents, or track weight loss progress as a percentage of starting weight.
For more advanced mathematical operations beyond percentages — like trigonometry, logarithms, or exponents — our scientific calculator online handles the full range of functions you would find on a physical scientific calculator, right in your browser.
This percentage calculator is built with plain JavaScript and runs entirely in your browser. No data is transmitted to any server, so your numbers remain private. The tool uses standard floating-point arithmetic and rounds results to a reasonable number of decimal places for readability. It works on all modern browsers across phones, tablets, and desktop computers without requiring any installation or plugin.