Percentage Calculator

Real-world percentage calculations for shopping, tips, grades, and business.

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In the US, 15-20% is standard for sit-down restaurants. 18% is common for parties of 6+. For delivery, 15-20% of the order total is typical.
Standard US grading: A = 90-100%, B = 80-89%, C = 70-79%, D = 60-69%, F = below 60%. Some schools use +/- grades (e.g., A- = 90-93%).
Percentage change is always relative to the original value. A 50% increase followed by a 50% decrease does NOT return to the original — it results in a 25% net decrease.
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Markup and margin are NOT the same. Markup is profit divided by cost. Margin is profit divided by selling price. A 100% markup = 50% margin.
Markup = (Selling Price - Cost) / Cost x 100
Answers: "How much did I add on top of my cost?"

Margin = (Selling Price - Cost) / Selling Price x 100
Answers: "What percentage of the selling price is profit?"

Example: Buy for $10, sell for $20
Markup = ($20-$10)/$10 = 100%
Margin = ($20-$10)/$20 = 50%
Same dollar profit, very different percentages.
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How to Use This Percentage Calculator

Select a mode from the tabs above — Shopping, Tip, Grade, Change, Margin, or General. Each mode is built for a specific real-world scenario, so you get the right inputs and outputs without translating your problem into abstract math. Enter your numbers and results update instantly. Click the copy button on any result to copy it to your clipboard.

Shopping mode handles discount calculations including stacked discounts (multiple discounts applied sequentially). Tip mode shows four common tip percentages side by side so you can choose quickly. Grade mode converts your raw score into a percentage and letter grade. Change mode calculates percentage increase or decrease between two values. Margin mode shows both markup and margin simultaneously to prevent the most common business calculation mistake. General mode covers any percentage calculation that doesn't fit the other categories.

Understanding Percentages in Everyday Life

Percentages appear everywhere — price tags, restaurant checks, report cards, pay stubs, investment returns. The word "percent" literally means "per hundred," so 25% means 25 out of every 100. Despite being simple in concept, percentages trip people up because they behave differently than whole numbers in certain contexts.

For instance, a 50% increase followed by a 50% decrease does not bring you back to the starting value. If you start with $100, a 50% increase gives you $150, but a 50% decrease of $150 gives you $75 — a net loss of 25%. This is because each percentage is calculated relative to a different base. Understanding this distinction is the key to avoiding common percentage mistakes.

Common Percentage Mistakes to Avoid

Stacking discounts incorrectly: A 30% discount followed by a 20% discount is NOT the same as a 50% discount. The second discount applies to the already-reduced price, so the total discount is actually 44%. Our Shopping mode shows this breakdown clearly so you never overpay expecting a bigger discount than you're actually getting.

Confusing markup and margin: If a product costs $10 and sells for $20, the markup is 100% (you doubled the cost) but the margin is 50% (half the selling price is profit). Many businesses lose money because they set prices based on the wrong percentage. Our Margin mode shows both numbers side by side to prevent this confusion.

Percentage points vs. percentages: If an interest rate goes from 5% to 7%, it increased by 2 percentage points but 40% in relative terms. These are very different things, and news headlines often mix them up. When comparing rates, be clear about which measurement you mean.

Privacy

This tool runs entirely in your browser. No data is sent to any server. All calculations happen locally using JavaScript, and your calculation history is stored only in your browser's local storage. Clear your browser data at any time to remove it.

Read the story behind this tool: Why I Built a Percentage Calculator When Google Already Answers "20% of 150"