Percentage
Calculator
Calculate percentages, discounts, increases, decreases, and reverse percentages instantly — five calculation modes in one clean tool.
Percentage Calculator: Calculate Percentages Easily
Percentages appear in virtually every area of daily life — shopping discounts, tax calculations, salary increases, investment returns, exam scores, nutrition labels, and statistical analysis. Yet many people struggle with percentage calculations beyond the basics. This free percentage calculator covers five essential percentage calculation types in a single tool, with real-time results and the formula used for each calculation shown clearly, so you understand the math behind every answer.
Quick reference: 20% of 150 = 30 · A price rising from $200 to $250 = 25% increase · $40 is 25% of $160 · A 30% discount on $89.99 saves $27.00 · The difference between 80 and 100 is 22.2% (percentage difference). Use the tabs above for any of these calculations instantly.
The Five Percentage Calculation Types
| Mode | Question it answers | Formula | Example |
|---|---|---|---|
| % of Number | What is X% of Y? | (X ÷ 100) × Y | 20% of 150 = 30 |
| % Change | How much did it change? | ((New − Old) ÷ Old) × 100 | $200 → $250 = +25% |
| % Difference | How different are two values? | (|A−B| ÷ avg) × 100 | 80 vs 100 = 22.2% |
| Reverse % | X is Y% of what? | X ÷ (Y ÷ 100) | 40 is 25% of 160 |
| Discount | What’s the sale price? | Price × (1 − Disc%÷100) | 30% off $90 = $63 |
How to Calculate Percentage of a Number
The most fundamental percentage calculation: finding X% of Y. The formula converts the percentage to a decimal (dividing by 100) then multiplies by the number:
Formula: Result = (Percentage ÷ 100) × Number
Examples:
• 15% of 200 = (15 ÷ 100) × 200 = 0.15 × 200 = 30
• 8.5% sales tax on $120 = 0.085 × 120 = $10.20
• 20% tip on a $65 restaurant bill = 0.20 × 65 = $13.00
How to Calculate Percentage Increase and Decrease
Percentage change measures how much a value has grown or shrunk relative to its starting point. This is one of the most commonly misunderstood calculations — many people confuse absolute change (the numerical difference) with relative change (the percentage).
Formula: % Change = ((New Value − Original Value) ÷ Original Value) × 100
Positive result = increase | Negative result = decrease
Examples:
• Salary: $50,000 → $55,000: ((55,000 − 50,000) ÷ 50,000) × 100 = +10% increase
• Stock: $180 → $144: ((144 − 180) ÷ 180) × 100 = −20% decrease
• Website traffic: 1,200 → 1,560 sessions: +30% increase
Percentage Difference vs Percentage Change
These two concepts are often confused but are mathematically different:
- Percentage change uses one value as the reference base (the “before” value). It’s directional — a change from $100 to $120 is +20%, but the reverse (from $120 to $100) is −16.7%, not −20%.
- Percentage difference compares two values symmetrically using their average as the denominator. The result is the same regardless of which value is A or B. Used in scientific comparisons where neither value is definitively the “original.”
Real-Life Percentage Uses
Shopping discounts
Use the Discount tab to instantly calculate final prices after percentage-off sales. A 40% discount on a $250 item saves $100, bringing it to $150 — but an additional 10% loyalty coupon applies to $150, not the original $250.
Business KPIs
Monthly revenue growth, customer retention rate, conversion rate improvement, and cost-of-goods-sold as a percentage of revenue all use the % Change formula. Quarter-over-quarter and year-over-year comparisons are percentage change calculations.
Finance and investing
Investment returns, savings account interest, inflation rates, and portfolio allocation percentages all rely on basic percentage arithmetic. A 7% annual return compounded means your money doubles approximately every 10 years (72 ÷ 7 = 10.3 years — the Rule of 72).
Tax calculations
VAT/GST, income tax brackets, and withholding tax all use percentage calculations. Reverse percentage is crucial here: if you paid $115 including 15% GST, the pre-tax price was $115 ÷ 1.15 = $100 — not $115 − 15% of $115.
Common Percentage Mistakes
- Applying discounts sequentially incorrectly: A 20% then 10% discount is not a 30% discount — it’s 28%. Always apply each percentage to the running total: $100 → $80 (−20%) → $72 (−10%).
- Confusing percentage change direction: A 50% increase followed by a 50% decrease does not return to the original — you end at 75% of start. $100 × 1.5 = $150 × 0.5 = $75.
- Using wrong base for percentage change: A quantity that goes from 1,000 to 1,200 is a 20% increase. But going from 1,200 back to 1,000 is only a 16.7% decrease — the base is different.
- Reversing tax incorrectly: To find pre-tax price from a tax-inclusive amount, divide by (1 + tax rate), don’t subtract the tax rate percentage from the total.
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Frequently Asked Questions
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