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How to Calculate Percentage — Formulas, Examples & Calculator

Percentage calculations are essential in everyday life—from working out store discounts and restaurant tips to calculating taxes, markups, investment yields, and academic grades. Despite their simplicity, confusing percentage points with relative changes or applying the wrong formula can lead to costly mistakes. This comprehensive guide details all 5 fundamental percentage formulas, provides practical everyday examples, and shows you how to use our free percentage calculator.

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The 5 Core Percentage Formulas

Virtually every percentage problem can be solved using one of these five mathematical formulas: ════════════════════════════════════════════════════════ FORMULA 1 — What is X% of Y? Formula: Result = (X ÷ 100) × Y Example: What is 15% of 200? = (15 ÷ 100) × 200 = 0.15 × 200 = 30 FORMULA 2 — X is what % of Y? Formula: Percentage = (X ÷ Y) × 100 Example: 30 is what % of 200? = (30 ÷ 200) × 100 = 0.15 × 100 = 15% FORMULA 3 — Percentage change (Increase / Decrease) Formula: Change% = ((New Value - Old Value) ÷ Old Value) × 100 Example: Price increased from €80 to €100 = ((100 - 80) ÷ 80) × 100 = (20 ÷ 80) × 100 = 25% increase FORMULA 4 — Add percentage to a number (Markup / Sales Tax) Formula: Result = Number × (1 + Percentage ÷ 100) Example: €500 + 20% = 500 × (1 + 0.20) = 500 × 1.20 = €600 FORMULA 5 — Remove percentage from a number (Reverse Percentage) Formula: Result = Number ÷ (1 + Percentage ÷ 100) Example: €600 with 20% tax included = 600 ÷ 1.20 = €500 ════════════════════════════════════════════════════════

Real-Life Examples & Everyday Applications

Here is how these five formulas apply to common financial and daily scenarios:

Scenario	Starting Values	Applied Formula	Final Result
Store Discount	Shirt €60 with 30% off	60 × (1 − 0.30)	Sale price: €42 (saved €18)
Restaurant Tip	Bill €85, want to tip 15%	85 × 0.15	Tip amount: €12.75 (total €97.75)
Salary Increase	Current salary €45,000, 6% raise	45,000 × 1.06	New salary: €47,700 (+€2,700)
Exam Score	42 correct answers out of 50	(42 ÷ 50) × 100	Final grade: 84%
Price Drop (Inflation relief)	Laptop dropped from €1,200 to €960	((960 − 1200) ÷ 1200) × 100	Discount: 20% reduction

Common Percentage Pitfalls to Avoid

Many people encounter mistakes when compounding or reversing percentages: 1. Asymmetry of Gains and Losses: If an investment drops by 50%, it requires a 100% gain—not 50%—to return to its starting value. 2. Consecutive Percentages: Applying two 10% discounts in a row does not equal a 20% discount. €100 minus 10% is €90; €90 minus 10% is €81 (total discount: 19%). 3. Percentage Points vs. Percentages: If an interest rate climbs from 2% to 3%, it increased by 1 percentage point, but by 50% in relative terms.

How to Use Our Percentage Calculator

Perform any percentage operation in seconds with zero manual math:

Step 1: Choose calculation mode

Select your desired mode: percentage of a number, percentage change, or markup/discount.

Step 2: Enter values

Enter your primary number and percentage rate into the clearly labeled fields.

Step 3: Instant calculation

The calculator updates results automatically in real time as you type.

Step 4: Copy answer

Click the Copy button to immediately save the calculated result to your clipboard.

Frequently Asked Questions

How do I calculate 20% of a number?

To find 20% of any number, multiply the number by 0.20 (or divide by 5). For example, 20% of €150 is 150 × 0.20 = €30.

How do I calculate percentage increase?

Subtract the original value from the new value, divide the difference by the original value, and multiply by 100. Formula: ((New - Old) ÷ Old) × 100.

How do I remove a percentage from a price?

To remove an added percentage (such as VAT or sales tax), divide the total amount by (1 + percentage/100). For example, to remove 20% from €120, divide 120 by 1.20 = €100.

What is the percentage formula?

The baseline percentage formula is Percentage = (Part ÷ Whole) × 100. It expresses what proportion one quantity represents relative to a total baseline of 100.

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