How to Use the Percentage Calculator
This calculator offers 4 different modes for common percentage calculations. Simply select the mode that matches your need:
- % of Number: Calculate what X% of Y equals (e.g., "What is 15% of 200?")
- What Percent: Find what percentage one number is of another (e.g., "30 is what % of 200?")
- % Change: Calculate percentage increase or decrease (e.g., "100 increased by 20%")
- Reverse %: Find the original number when you know the percentage (e.g., "30 is 15% of what?")
Common Use Cases
🛍️ Shopping Discounts
Calculate the final price after a discount. If something costs $50 and has a 20% discount, use "% Change" mode with decrease.
🍽️ Restaurant Tips
Calculate how much to tip. If your bill is $80 and you want to leave 15%, use "% of Number" mode.
💰 Sales Tax
Add sales tax to a price. If an item costs $100 and tax is 8%, use "% Change" mode with increase.
📊 Grade Percentages
Calculate your test score. If you got 42 out of 50 questions correct, use "What Percent" mode.
Percentage Formulas
Finding X% of Y
Result = (X ÷ 100) × Y
Example: 15% of 200 = (15 ÷ 100) × 200 = 30
Finding What % X is of Y
Result = (X ÷ Y) × 100
Example: 30 is what % of 200? = (30 ÷ 200) × 100 = 15%
Percentage Increase/Decrease
Result = Original ± (Original × Percentage ÷ 100)
Example: 100 increased by 20% = 100 + (100 × 20 ÷ 100) = 120
🔒 Privacy & Security
Your privacy is safe with us. All percentage calculations are performed locally within your browser. No numeric entries, financials, or inputs are ever sent to our servers. Learn more in our Privacy Policy.
📖 What is a Percentage and How Does it Work?
A percentage is a dimensionless ratio that expresses a fraction of 100. The word is derived from the Latin phrase per centum, which literally translates to "by the hundred." The percentage symbol is %.
For example, 25% represents 25 parts out of 100, which is equivalent to the decimal 0.25 or the simplified fraction 1/4. Percentages are widely used in daily life to express sales tax, shopping discounts, bank interest rates, and statistical proportions.
Common Percentage to Fraction/Decimal Conversions
| Percentage | Decimal Equivalent | Fraction Equivalent |
|---|---|---|
| 10% | 0.1 | 1/10 |
| 20% | 0.2 | 1/5 |
| 25% | 0.25 | 1/4 |
| 50% | 0.5 | 1/2 |
| 75% | 0.75 | 3/4 |
| 100% | 1.0 | 1/1 |
Understanding Compounding Discounts
A common pitfall in calculating percentages is adding up consecutive percentage rates. For instance, if a store offers an additional 20% discount on an item that is already marked down by 30%, the final discount is not 50%. Instead, the calculations are applied sequentially:
- Apply the first 30% discount to the original $100 price, which reduces it to $70.
- Apply the additional 20% discount to the new $70 value: 20% of $70 is $14.
- The final price becomes $70 - $14 = $56, which represents a total discount of 44% from the original price.
❓ FAQ
How do I calculate a discount percentage? ▼
Use the "% Change" mode and select "Decrease". Enter the original price and the discount percentage. For example, a $100 item with 20% off would give you $80 as the final price.
What's the difference between percentage and percentile? ▼
A percentage is a fraction of 100 (e.g., 50% = 50/100). A percentile is a statistical measure indicating the value below which a percentage of data falls (e.g., 90th percentile means you scored better than 90% of others).
Is my data saved or sent to a server? ▼
No. All calculations happen entirely in your browser. Your numbers never leave your device, ensuring complete privacy.
Can I calculate multiple discounts? ▼
Yes, but apply them sequentially. For example, for 20% off then 10% off a $100 item: First calculate $100 - 20% = $80, then calculate $80 - 10% = $72. Note that this is NOT the same as 30% off!