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Percentage calculations are among the most frequently performed mental arithmetic operations in daily life — yet they are also among the most frequently botched. Whether you are calculating a restaurant tip, figuring out how much you save in a sale, determining a mortgage rate's monthly impact, or trying to understand whether your investment has grown by 12% or shrunk by 8%, percentage errors are both common and costly. Our percentage calculator eliminates that risk entirely by offering five dedicated calculation modes in a single, instantly accessible interface: X% of Y (the classic percentage-of-a-number), Percentage Change (increase or decrease from A to B), X is what % of Y (reverse percentage), Add a percentage (price after markup or tax), and Subtract a percentage (price after discount). Each mode shows the complete formula alongside the result, so you always understand the calculation — not just the answer.

Percentage calculations and tip calculations are closely related daily financial operations — both involve applying a percentage rate to a base number. Our dedicated Tip Calculator goes further for dining specifically: it handles bill splitting among multiple people, calculates each person's share including tip, and accounts for different tipping conventions across countries — making it the more contextually appropriate tool for restaurant scenarios, while our percentage machine handles every other percentage challenge with equal versatility.

For those building stronger numeracy skills, percentage and prime number theory are two foundational pillars of number sense that reinforce each other. Our Prime Number Checker offers a fascinating complement: it reveals the prime factorisation of any composite number — which is, at its core, the mathematical equivalent of breaking a number down to its most fundamental percentage components. Together, these two tools make an excellent mathematical toolkit for students, educators and lifelong learners.

Five essential percentage calculations everyone uses

Our Percentage Machine offers five dedicated modes covering the complete landscape of real-world percentage problems: (1) X% of Y — the classic percentage-of-a-number (a 20% discount on a €150 item = €30). (2) Percentage Change — going from one value to another as a percentage (a salary increasing from €40,000 to €45,000 = 12.5% increase). (3) X is what % of Y — finding the percentage that one number represents of another (87 correct answers out of 120 = 72.5%). (4) Add % to a number — applying a markup or tax (€100 + 21% VAT = €121). (5) Subtract % from a number — applying a discount or reduction (€200 − 15% = €170). Each mode shows the full formula so you understand the calculation, not just the answer.

Compound percentage change: a common misconception

If a price increases by 25% and then decreases by 25%, most people assume the net change is zero. It is not: a 25% increase to €100 gives €125, then a 25% decrease gives €93.75 — a net loss of 6.25%. This is because percentage changes are multiplicative, not additive. This same principle applies to investment returns, inflation and compound interest. For all restaurant-specific percentage work, our dedicated Tip Calculator handles bill splitting and cultural tipping norms by country.