Fitness and Nutrition Guides

What these guides are for

A calculator gives you a number. It does not tell you whether the number is worth acting on, how wide its error bars are, or what to do when reality disagrees with it — and those are usually the parts that decide whether anything changes. A protein calculator can return 140 grams a day without telling you that the range beneath that figure is genuinely wide, that the daily total matters far more than how you split it across meals, or that pushing well past the target mostly just displaces the rest of your food. That context is what these guides carry.

Each one is written to be read on its own, without the calculator open. They explain where the formula came from, what it assumes about you, the size of the gap between the estimate and the measurement, and what to do when your own data says something different. Where the honest answer is "this is uncertain," that is what the guide says rather than the more confident-sounding alternative.

How they fit with the calculators and charts

The three formats answer three different shapes of question, and it is worth knowing which one you want. A calculator answers one question for one person: enter your details, get your figure. A reference chart shows the whole range at once, which is what you want when you are comparing options rather than looking yourself up — there are 13 of them. A guide explains the reasoning, which is what you want before you decide the number matters.

Every guide below names the calculator it goes with, so you can read the explanation and then run your own numbers without hunting for the right tool.

How they are written

Every guide ends with its sources: the actual papers and position statements behind the claims, named and linked where a public link exists, rather than a vague appeal to research. Where a familiar rule of thumb has no good evidence behind it, the guide says so and explains where the rule came from — the "eight glasses of water a day" advice is a worked example of exactly that. All of them are written and reviewed by Jesse, who is not a doctor or a dietitian and says so on every page, and each carries the date it was last reviewed. The methodology page documents every formula the site uses and its known limitations.

These are educational explainers for healthy adults, not medical advice. If you are pregnant, managing a medical condition, taking medication that affects appetite or fluid balance, or have a history of disordered eating, the right next step is a qualified professional who can examine you — not a web page.