Calculator and Tool Methodology
The value of a calculator lies less in the number it gives than in its ability to say how that number was found. This page explains the principles behind the tools on this site and how to read their results.
Key points
- Every tool discloses its formula and assumptions on its own page
- Results are estimated ranges, not measurements or medical assessments
- Data you enter stays in your browser and is not sent to a server
- Tools are covered by our corrections policy; errors can be reported
Formulas are disclosed
None of our tools is a black box. On each tool's page we explain which formula or method it uses, what assumptions that formula rests on, and in which situations it can mislead. We prefer widely accepted, published formulas; we never present a calculation method of our own invention as a "scientific formula". If you find a tool's methodology note insufficient, that is a gap worth reporting to us.
Results are estimates, not verdicts
General formulas are built on averages; they know nothing of your metabolism, your health history or your circumstances. That is why tool outputs use the language of "estimated range" and "starting point": the same result for the same inputs can correspond to two different real needs in two different people. Health-related tool outputs are never a diagnosis, a treatment or a personal prescription; the reasons for that limit are set out in our Health Content Policy. For important decisions, the right partner is a professional who can interpret the result with you.
Your data stays in your browser
Values you enter into our tools, such as age, height and weight, are not sent to our servers; the calculations run on your own device, inside your browser. If a tool remembers your results for a later visit, that information is kept only in your browser's local storage; you can delete it at any time by clearing your browser's site data. The full picture is described in our Privacy and Data Approach.
Limits, edge cases and upkeep
Formulas have ranges of validity; at extreme inputs, very low or very high, their reliability drops. We aim to define sensible input ranges in our tools and to warn you when a value falls outside them. We review tools in line with updates to their underlying sources and with reported errors; that routine is part of our Freshness and Maintenance Policy. If you spot an incorrect result, you can report it through our Corrections Policy.
A working version
This policy is a working version. As new tools are added and existing ones evolve, this page will be updated. Questions about methodology help us find the weakest point of our tools; please do not hold back.