Percentage change, discounts, tax, tips and everyday percent-of-number questions. Use the calculators for your own numbers and the guides for formulas, examples and common questions.
Use the tool that matches the exact problem you need to solve.
Solve common percentage questions: find a percentage of a number, determine what percent one number is of another, and calculate a value from a known percentage.
Calculate percentage increase or decrease from an original value to a new value.
Calculate symmetric percent difference between two values without treating either one as the original value.
Calculate percent error between an experimental or measured value and an accepted value.
Calculate a sale price, amount saved and optional final price after sales tax.
Calculate sales tax and the final purchase total from a pre-tax price and tax rate.
Calculate a tip, total bill and per-person amount when splitting a restaurant or service bill.
Three long-tail answers that explain formulas and common scenarios behind this calculator cluster.
Learn the percentage increase and decrease formulas, see worked examples, and avoid common mistakes when comparing an old value with a new value.
Read guide →Percentages, Discounts & Sales TaxSee the formula for a 20% discount on $100 and learn how to calculate any discounted sale price.
Read guide →Percentages, Discounts & Sales TaxLearn the sales-tax formula and how to calculate the tax amount and final purchase total.
Read guide →Percentage change, discounts, tax, tips and everyday percent-of-number questions. The pages in this cluster are intentionally connected: calculator pages handle the arithmetic, while the guides answer informational searches, show worked examples and explain how to interpret the result.
Use the examples as reference points, then open a calculator and substitute your own values. For decisions involving contracts, taxes, health, payroll rules, construction requirements or other high-stakes details, verify the real-world assumptions with an appropriate authoritative source.
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