Frequently Asked Questions

To calculate a percentage of a number, multiply the number by the percentage divided by 100. For example, to find 25% of 200, calculate 200 x (25/100) = 200 x 0.25 = 50. On our calculator, simply enter 25 in the percentage field and 200 in the value field under the Basic % tab.

Margin and markup both measure profit but from different perspectives. Margin is the profit expressed as a percentage of the selling price. Markup is the profit expressed as a percentage of the cost price. For example, if you buy an item for $60 and sell it for $100, your profit is $40. Your margin is 40/100 = 40%, while your markup is 40/60 = 66.67%. Margin is always smaller than markup when both are positive.

Percentage change is calculated using the formula: ((New Value - Old Value) / |Old Value|) x 100. For example, if a stock price goes from $80 to $100, the percentage change is ((100 - 80) / 80) x 100 = 25% increase. If it goes from $100 to $80, the change is ((80 - 100) / 100) x 100 = -20% decrease. Note that the percentage is different in each direction because the base value changes.

In the United States, the standard tip for sit-down restaurant service is 15-20% of the pre-tax bill. 15% is considered the minimum for adequate service, 18% is standard for good service, 20% is common for very good service, and 25% or more is appropriate for exceptional service. For takeout orders, 10% is typical. For delivery, 15-20% is standard. Our tip calculator makes it easy to compute any percentage and split the bill among multiple people.

Yes, absolutely. All calculations are performed entirely within your web browser using client-side JavaScript. No numbers, financial data, or calculation inputs are ever transmitted to our servers or any third party. Your calculation history is stored only in your browser session and is cleared when you close the page. We do not require any account creation or personal information to use the tool.

The natural language input bar at the top of the calculator understands questions written in plain English. You can type phrases like "What is 15% of 200?", "25 out of 80", "45 is what percent of 90?", or "Change from 100 to 150". The parser recognizes common patterns and automatically selects the correct calculation mode. Click the suggestion buttons below the input for examples of supported formats.

While our calculator focuses on single-step percentage calculations, you can use it to compute compound percentages by chaining calculations. For example, to calculate a 10% increase followed by a 20% increase on $100, first calculate 10% of 100 (which is $110), then calculate 20% of 110 (which is $132). The total compound increase is 32%, not 30%, because the second percentage is applied to the already-increased amount.

Stacked discounts are not additive. A 20% discount followed by an additional 10% discount does not equal 30% off. Instead, calculate sequentially. If an item is $100 with 20% off, the price becomes $80. Then applying 10% off to $80 gives you $72, meaning the total effective discount is 28%, not 30%. Use the Discount Calculator mode to verify each step.

The tip formula is: Tip Amount = Bill Amount x (Tip Percentage / 100). For a $85 bill with an 18% tip: $85 x 0.18 = $15.30. The total bill would be $85 + $15.30 = $100.30. If splitting among 3 people, each person pays $100.30 / 3 = $33.43. Our tip calculator handles all of this automatically, including bill splitting.

Once the page has loaded in your browser, all calculation functionality works without an internet connection. The calculator uses only client-side JavaScript, so no server communication is needed for any computation. However, you will need an initial internet connection to load the page, and some features like font loading may not work offline.