Free Online Percentage Calculator

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How to Use This Percentage Calculator

  1. Pick your calculation modeOur Percentage Calculator makes percentage math effortless with three calculation modes. Select your mode from the tabs at the top of the tool.
  2. Mode 1: What is X% of Y?Enter the percentage value and the number you want to calculate against. For example, enter 15 and 200 to find that 15% of 200 is 30. This is perfect for calculating discounts, tips, or tax amounts. Use the quick-select buttons for common percentages.
  3. Mode 2: X is what % of Y?Enter two numbers to find the percentage relationship between them. For example, enter 30 and 200 to discover that 30 is 15% of 200. Use this for grades, completion rates, or performance metrics.
  4. Mode 3: Percentage ChangeEnter the original value and the new value to calculate the increase or decrease. For example, from 200 to 250 gives a 25% increase. Ideal for tracking price changes, growth rates, or year-over-year comparisons.
  5. Copy and reuse your resultsResults appear instantly as you type. Click "Copy Result" to copy the formatted calculation to your clipboard. Your recent calculations are saved during your session for easy reference.

All calculations happen entirely in your browser - nothing is sent to any server.

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What is a Percentage?

A percentage is a mathematical expression representing a fraction of 100. The word comes from the Latin "per centum," meaning "by the hundred." When you see 45%, it means 45 out of every 100, or the fraction 45/100, which equals 0.45 as a decimal. A percentage calculator lets you work out these ratios instantly — no paper, no long division, no mental math.

Where percentages show up in daily life

Percentages are one of the most commonly used mathematical concepts in daily life. They appear in financial contexts like interest rates, tax calculations, and discount pricing. A 20% discount on a $50 item means you save $10, paying only $40. Banks express loan interest as annual percentage rates (APR), allowing you to compare borrowing costs across different lenders.

Percentages in business and investing

In business, percentages measure performance through metrics like profit margins, growth rates, and market share. A company growing revenue from $1 million to $1.2 million has achieved 20% growth. Investors track percentage returns to evaluate portfolio performance regardless of the dollar amounts invested.

Percentage change for spotting trends

Percentage change formula ((New Value − Old Value) / Old Value) × 100

Percentage change calculations are particularly important for understanding trends. A positive result indicates an increase, while a negative result shows a decrease. This applies whether you're tracking stock prices, population growth, or website traffic.

Percentages vs. percentage points

Understanding the difference between percentage points and percentages matters too. If an interest rate moves from 5% to 7%, that's a 2 percentage point increase but a 40% relative increase. This distinction frequently appears in economic reporting and financial analysis, where precision in language affects interpretation.

Percentage Formulas You Can Use

The three percentage modes in this calculator cover almost every real-world percentage problem. Here are the formulas behind them:

Percentage of a number Part = (Percent ÷ 100) × Whole. Example: 15% of 200 = (15 ÷ 100) × 200 = 30.
What percentage A is of B Percent = (A ÷ B) × 100. Example: 30 of 200 = (30 ÷ 200) × 100 = 15%.
Percentage increase ((New − Old) ÷ Old) × 100. Example: from 50 to 65 = ((65 − 50) ÷ 50) × 100 = 30% increase.
Percentage decrease ((Old − New) ÷ Old) × 100. Example: from 80 to 60 = ((80 − 60) ÷ 80) × 100 = 25% decrease.
Reverse percentage (original price) Original = Final ÷ (1 − Discount ÷ 100). Example: a $80 item after 20% off was originally $80 ÷ 0.80 = $100.
Markup ((Sale − Cost) ÷ Cost) × 100. Example: buying at $40, selling at $60 = 50% markup.
Profit margin ((Revenue − Cost) ÷ Revenue) × 100. Used for gross and net margin calculations.

Common Use Cases for a Percentage Calculator

  • Shopping discountsWork out how much you save on 20% off, 30% off, or 70% off sale items before you buy.
  • Sales tax, VAT, and GSTCalculate the tax added to a purchase in any country or state.
  • Tip calculationsFigure 15%, 18%, or 20% of a restaurant bill quickly; split-the-check is available in our Tip Calculator.
  • Test scores and gradesConvert raw marks (e.g., 42/50) into a percentage grade for school, university, and certifications.
  • Business KPIsGrowth rate, conversion rate, bounce rate, churn rate, click-through rate (CTR), and open rate.
  • Investment returnsCalculate percent gain or loss on stocks, crypto, ETFs, and mutual funds.
  • Fitness and weight goalsMeasure body-fat percentage change or progress toward a weight-loss target.
  • Tip, commission, and bonusCalculate sales commission, real-estate agent fees, and year-end bonuses.
  • Cooking and recipesScale ingredients up or down by a percentage for larger or smaller batches.
  • Project completionTrack progress as a percentage of tasks done vs. tasks remaining.

Percentage Calculation Tips

  • 10% shortcut10% of any number is that number with the decimal point moved one place left. 10% of 240 = 24.
  • Double for 20%, halve for 5%Once you know 10%, 20% is double, 5% is half. Great for quick tip math.
  • Commutative trickX% of Y always equals Y% of X. So 4% of 75 = 75% of 4 = 3 — pick whichever is easier.
  • Stacked discounts don't add20% off + 10% off is 28% off, not 30% (0.80 × 0.90 = 0.72). Use the calculator in two steps.
  • Percent vs. percentage pointsA move from 4% to 5% is "1 percentage point" or a "25% relative increase." Use the right phrasing in reports.
  • Round sensiblyFor money use two decimals; for percentages one decimal is usually enough.

Frequently Asked Questions

How do I calculate a percentage of a number?
Multiply the number by the percentage and divide by 100. For example, 25% of 80 equals 80 × 25 ÷ 100 = 20. Alternatively, convert the percentage to a decimal (0.25) and multiply: 80 × 0.25 = 20. Our calculator handles this instantly.
How do I find what percentage one number is of another?
Divide the first number by the second and multiply by 100. For example, if 15 is what percent of 60: (15 ÷ 60) × 100 = 25%. Use our "X is what % of Y?" mode for instant results.
How do I calculate percentage increase or decrease?
Subtract the old value from the new value, divide by the old value, then multiply by 100. If a price goes from $40 to $50: ((50-40) ÷ 40) × 100 = 25% increase. Negative results mean a decrease.
What is the difference between percentage and percentage points?
Percentage points measure the arithmetic difference between two percentages. If interest goes from 3% to 5%, that is 2 percentage points but a 66.7% relative increase. Percentage points are absolute, while percentage change is relative.
Can I calculate reverse percentages with this tool?
Yes. Use the "X is what % of Y?" mode in reverse. If an item costs $80 after a 20% discount, the original price was $80 ÷ 0.80 = $100. Enter values to find the original amount before a percentage was applied.
How do I calculate a discount or sale price?
Use the "What is X% of Y?" mode. Enter the discount percentage and the original price to get the savings amount, then subtract from the original price. Example: a 30% discount on $120 is $36, so the sale price is $84.
How do I calculate tax, VAT, or GST on a price?
Enter the tax rate (for example 8.25%, 20%, or 18%) and the pre-tax amount in the "What is X% of Y?" mode. The result is the tax amount — add it to the original price for the final total. Works for sales tax, VAT, GST, and service charges.
How do I calculate a grade or test score percentage?
Use the "X is what % of Y?" mode. Enter the points earned and the total points possible. Example: scoring 42 out of 50 gives (42 ÷ 50) × 100 = 84%. The calculator instantly converts raw marks into a percentage grade.
How do I calculate tip percentage on a bill?
Use "What is X% of Y?" with the tip rate (15%, 18%, or 20%) and the bill amount. For a dedicated tool with split-the-bill support, see our Tip Calculator.
How do I calculate year-over-year (YoY) percentage growth?
Use the Percentage Change mode. Enter last year's value as the original and this year's value as the new — the result is your YoY growth (or decline) as a percentage. Great for revenue, traffic, KPIs, and investment returns.
Is the percentage calculator free and mobile friendly?
Yes — the percentage calculator is 100% free, works on phones, tablets, and desktops, and runs entirely in your browser. No signup, no account, no data ever leaves your device.
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Want a deeper dive? Read our complete percentage guide with worked examples for tips, discounts, raises, and grades. Read the percentage guide →
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