Methodology: how our tools calculate
Every tool applies published formulas, explained in plain text on its page. Rates and tables, such as tax brackets and holidays, are dated, sourced and reviewed every year. Calculations run in your browser, so your data is not sent anywhere.
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Formulas written in plain language
Each calculator shows its method below the result: the formula, a reference table and three worked examples. You can check any answer by hand. We do not invent formulas. When a rule is official we apply it as written. When it is not (a horoscope or a username generator, for example), the tool says so.
Rates, tables and sources
Values that change over time are not hard-coded. Each tool keeps them in its own configuration file, and each file carries:
- the last-updated date of the values, shown on the tool page;
- the source: the official text, the table published by the agency concerned, or the official calendar.
When do we update?
| Type of data | Review schedule | Examples |
|---|---|---|
| Tax and payroll tables | Every January, and whenever a mid-year change is announced | Federal tax brackets, standard deduction, FICA rates |
| Calendars | Every year | Federal holidays, week numbers |
| Formats and standards | Whenever they change | Passport photo size, paper sizes, SMS limits |
| Fixed formulas | Reviewed each time a tool is edited | BMI, percentages, unit conversions |
Everything runs in your browser
Calculations and text, PDF and image conversions run on your own device. Nothing is sent to our servers, except for a few conversions that cannot run locally (Word to PDF, for example). In that case the page tells you, and the file is deleted automatically after 1 hour without being read. See the privacy policy for details.
Testing and verification
The calculation logic of each tool is tested on normal cases, edge cases and invalid input before it goes live. The examples on each page are recomputed with the tool itself.
Limits you should know about
- Financial, legal and tax results are estimates only and do not replace professional advice.
- Health tools are not a substitute for a doctor's advice.
- Entertainment tools (horoscope, personality) are meant for fun.
- The AI text detector is heuristic: it estimates, it does not prove anything.
Found a mistake? Tell us
If you spot an outdated value or a suspicious result, report it from the contact page with the tool name and the values you entered. We fix it quickly and update the date on the page.