Percentage Calculator
Percentage Calculator
Calculate percentages, fractions, and percentage changes.
Report Bug Percentages are the language of finance, shopping, and statistics. Whether you are calculating a 20% tip at a restaurant, figuring out a 30% discount on Black Friday, or analyzing a 5% raise in your salary, accurate percentage calculation is essential. The Percentage Calculator handles the three distinct types of percentage math, ensuring you never overpay or underestimate a cost again.
In the US market, where the "Sticker Price" is rarely the "Final Price," understanding how to stack percentages is a critical consumer skill.
➗ The Three Core Formulas
Most people get stuck because they apply the wrong logic to the situation. Here is the cheat sheet for the three most common scenarios:
2. % Change: [(New - Old) / Old] × 100
3. Reverse (Remove Tax): Total / (1 + decimal %)
Variables Defined:
- Percentage Change: Used for tracking growth or loss (e.g., Stock market).
- Reverse Percentage: Used to find the original price before tax was added.
🛍️ Scenario: The "Double Dip" (Discount + Tax)
In the US, Sales Tax is calculated after the discount is applied, not before. Let's look at buying a $1,000 Laptop with a 20% Discount and 8% Sales Tax.
| PAYMENT SUMMARY | |
|---|---|
| Original Price (MSRP) | $1,000.00 |
| (-) Less: 20% Discount | - $200.00 |
| SUBTOTAL (Taxable Amount) | $800.00 |
| (+) Add: 8% Sales Tax | + $64.00 |
| TOTAL DUE | $864.00 |
| Note: Tax is calculated on the $800 Subtotal, not the $1,000 Original Price. | |
Math Insight: A common mistake is to simply take 20% off and then add 8% back to the original. The order of operations matters. Always apply the discount first to lower your taxable base.
US Context: Tips and Taxes
- The 20% Tipping Standard: In US restaurants, 15% used to be standard, but post-2020, 18% to 22% is the expected norm for good service. Calculate this on the Pre-Tax subtotal to avoid tipping on the tax.
- "Percentage Points" vs. Percent: If a loan rate goes from 4% to 5%, it increased by 1 Percentage Point, but it increased by 25% in relative cost (1 is 25% of 4). This distinction is crucial in finance.
- Markup vs. Margin: As explained in business calculators, a 50% markup is NOT a 50% profit margin.
Frequently Asked Questions (FAQs)
What is the fastest way to calculate a 20% tip in my head?
Move the decimal point one place to the left to find 10%. Then double that number.
Example: Bill is $45.00. 10% is $4.50. Double it ($9.00). That's your 20% tip.
How do I remove tax from a total price?
You cannot just subtract the percentage. You must use division. If the total is $108 and tax is 8%, calculate: $108 / 1.08 = $100. If you just subtracted 8% of $108 ($8.64), you would get the wrong answer.
What is "Percentage Change"?
This measures growth or decline. If you bought a stock for $100 and it is now $150, the change is ($150 - $100) / $100 = 0.50, or 50% Increase. If it drops to $50, it is a 50% Decrease.
Can a percentage be more than 100%?
Yes. If a price triples (e.g., $10 to $30), it has increased by 200%. However, you generally cannot have a "decrease" of more than 100% (unless you owe money), as value stops at zero.
What is the difference between "Percent" and "Permille"?
Percent (%) means "per 100." Permille (‰) means "per 1,000." Permille is rarely used in the US except for Blood Alcohol Content (BAC) or specific scientific measurements.
