About
About this site
Most BMI calculators hand you a number and a category and stop there. That is the least useful part of the answer. This site exists to give the number and the context: what it means, where it fails, and which measurement to reach for instead.
What is here
14 calculators covering body mass index, body composition, energy expenditure and body-shape ratios, each paired with an explanation of the equation behind it and its known limitations. Every tool runs entirely in your browser.
How the numbers are produced
Every formula on this site lives in one shared, unit-tested module. The figure a calculator returns, the number quoted in an article, and the values in a reference table all come from the same code, so they cannot drift apart. Where a worked example appears in the text, an automated test asserts the calculator produces exactly that result.
Where multiple accepted formulas exist — ideal weight has four, lean body mass has three — the site shows all of them rather than picking one and presenting it as the answer. The disagreement between them is real information, and hiding it behind a single figure would imply a precision that does not exist.
What this site will not do
- Give medical advice. Nothing here is a diagnosis or a treatment recommendation. BMI is a screening measure; it was designed to describe populations, not to assess individuals.
- Store what you enter. Every calculation happens in your browser. Your height, weight and measurements are never transmitted to a server, because there is no server to transmit them to.
- Pretend to more precision than exists. Tape-based body-fat estimates carry an error of several percentage points. Where that is true, the site says so rather than printing a decimal place and letting you assume it is meaningful.
- Moralise about weight. The categories are reported as what they are — statistical bands with known blind spots.
How this is funded
The site is free and intended to be supported by display advertising. There is nothing to buy, no account to create, and no newsletter. If advertising is added, it will be disclosed here and on the privacy page, along with whatever data collection it involves.
Corrections
If a formula, figure or claim here is wrong, it should be fixed. Reach us via the contact page and say what is incorrect and what it should be.