Percentage calculations
The percentage calculators use the arithmetic formulas shown under each result. Values are calculated in the browser. Results are displayed with up to two decimal places for readability, but the formula line provides the calculation behind the displayed result.
Percentage change
The percentage-change tool is designed for a positive, non-zero starting value. From zero, a percentage change cannot be calculated because division by zero is undefined. From a negative starting value, a percentage can be mathematically produced but is often misleading in ordinary language; the tool therefore shows the actual difference and asks the reader to interpret it with context.
Discounts and tax
The discount tool applies each discount sequentially. An optional tax rate is applied after the discounts, solely as an arithmetic scenario. It does not know local tax laws, delivery fees, seller conditions, or whether an advertised pre-tax price is genuine. Verify real checkout totals and local requirements separately.
Time-zone planner
The planner maps a selected city to an IANA time-zone identifier and uses the browser’s Intl.DateTimeFormat implementation to display the current date, time, and current offset for that time zone. The working-hours overlap is a simple current-offset comparison using 09:00–17:00 local time. It does not confirm someone’s availability, future date-specific daylight-saving rules, or local holidays. Recheck recurring meetings around clock changes.
Data and privacy
Calculations and city selections run in the browser. The site does not require an account. See the Privacy Policy for information about the contact form, analytics, advertising technology, and hosting.
Corrections
If you find a formula error, city mapping issue, broken link, or unclear explanation, use the contact form. We review reports and update substantive corrections as needed.