Editorial policy and methodology
Health information should be easy to check. This page explains how we choose formulas, cite sources, protect users from unsafe results and keep pages accurate.
Choosing formulas and categories
We use methods that are published in peer-reviewed research or by recognised health bodies, such as the CDC, WHO, NIH, NHS, the American Heart Association and professional colleges. Where several formulas exist, we say which one we use and why. Where they disagree, we show more than one result or explain the difference.
Naming our sources
Every calculator page has a Sources list. Medical claims, formulas and category tables are tied to a named source. If we make an assumption of our own, such as the 90-minute sleep cycle length, we label it as an assumption rather than a fact.
Safety limits
Some results could push a person towards an unsafe choice, so the tools apply conservative rules:
- Calorie tools are for adults aged 18 and over and never suggest a target below 1,200 kcal a day for women or 1,500 kcal for men.
- Weight-loss targets are never more than 25% below estimated maintenance calories, and are limited to about 1 kg (2 lb) a week.
- If a BMI is below 18.5, the calorie tool does not offer weight-loss targets.
- Unusual inputs, such as extreme heights, weights or other readings, trigger a prompt to check the entry and speak with a doctor or dietitian.
- Tools on sensitive topics carry prominent notices and never replace a clinician's judgement.
These limits are our own editorial rules, designed to be cautious. They are not a clinical protocol.
Testing
We check each formula against hand-worked examples and automated tests, including edge cases such as category boundaries and safety limits, and we try every calculator in a browser on desktop and mobile layouts before it goes live.
Updates and corrections
We review calculators when the underlying guidance changes or when a reader reports a problem. To report an error, contact us and, if you can, include a link to a source. We correct confirmed mistakes promptly.
Who writes and reviews
Pages are written and maintained by the HealthFitnessHQ editorial team. We do not claim medical qualifications or that a clinician has reviewed an individual page. Our job is to explain published guidance clearly, not to practise medicine.
Independence
HealthFitnessHQ does not currently carry advertising or sponsored content. If that changes, ads will be labelled, kept separate from the content and will have no influence on calculator results, wording or the sources we cite.
Formulas and sources at a glance
| Calculator | Method |
|---|---|
| BMI Calculator | BMI = weight ÷ height²; adult cut-offs from the CDC and WHO, with optional WHO Asian-population action points. |
| BMR Calculator | Mifflin–St Jeor (default), revised Harris–Benedict and Katch–McArdle equations for resting energy expenditure. |
| Body Fat Percentage Calculator | US Navy circumference method (Hodgdon & Beckett, 1984) with American Council on Exercise body-fat categories. |
| Calorie Calculator (TDEE) | Mifflin–St Jeor resting energy × activity factor (TDEE), with goal targets built on 7,700 kcal per kg and safety floors. |
| Calorie Deficit Calculator | Mifflin–St Jeor maintenance calories, a deficit of about 7,700 kcal per kg, and safety floors (1,200/1,500 kcal, 25% below maintenance, 1 kg a week). |
| Ideal Weight Calculator | Healthy BMI range (18.5–24.9) plus the Devine, Robinson, Miller and Hamwi ideal body weight formulas. |
| Macro Calculator | Mifflin–St Jeor × activity for calories (with safety limits), then protein, carbohydrate and fat split using 4, 4 and 9 kcal per gram. |
| One-Rep Max (1RM) Calculator | Average of the Epley, Brzycki, Lombardi and O'Conner formulas, with reps limited to 12 and a percentage table based on the Brzycki equation. |
| Protein Calculator | Protein per kilogram of body weight by activity level, from the US RDA and sports-nutrition and older-adult position statements. |
| Sleep Calculator | Sleep planned in 90-minute cycles plus a 15-minute allowance to fall asleep (both assumptions); recommended hours from the CDC. |
Estimates only. For information only, not medical advice.