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.
6 focused guides and worked examples for this calculator cluster.
Learn how to calculate 15% off any price. Multiply by 0.15 for the discount, or multiply by 0.85 for the final sale price.
Read guide →Percentages, Discounts & Sales Tax20% off $100 saves you $20, making the final price $80. See the calculation and use our discount calculator for any price or percentage.
Read guide →Percentages, Discounts & Sales TaxLearn the percentage decrease formula with worked examples, denominator rules, percentage-point differences and an Excel or Google Sheets formula.
Read guide →Percentages, Discounts & Sales TaxUse the percentage increase formula with worked price, salary and number examples. Learn which value goes in the denominator and when percent change is undefined.
Read guide →Percentages, Discounts & Sales TaxLearn the sales-tax formula, calculate tax and total price, reverse sales tax, and see examples for common tax rates and discounts.
Read guide →Percentages, Discounts & Sales TaxFind the original whole when you know a result and the percentage. Example: if 45 is 30% of a number, the original number is 150.
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.
Continue into another connected area of the reference library.