Editorial Policy

This page describes how HealthTools researches, writes, sources and reviews what it publishes. It applies to both the calculators and the guides. We put it in public because a site that asks you to trust its numbers should be willing to explain how it arrived at them.

Our source hierarchy

Not all evidence is equal, and we rank it explicitly. When sources conflict, the one higher on this list wins.

1. Systematic reviews and meta-analyses. Where a question has been examined across many studies, the pooled result outranks any single paper. These sit at the top because they show whether a finding holds up when tested repeatedly and in different populations, rather than whether it appeared once.
2. Randomised controlled trials. The strongest single-study design for a causal claim, because randomisation is what separates an effect from a correlation. Sample size, duration and how closely the trial population resembles the reader all affect how much weight we give it.
3. Prospective cohort and observational studies. Often the only ethical way to study long-term diet, body composition or activity outcomes, and the source of most of what is known about risk thresholds. We report these as associations rather than causes, because that is what they are.
4. Position stands and clinical guidelines from recognised bodies. Guidance from organisations such as the World Health Organization, the American College of Sports Medicine, the American College of Obstetricians and Gynecologists, the European Food Safety Authority, the Institute of Medicine and its successor at the National Academies, the Centers for Disease Control and Prevention and the NHS. These are excellent for thresholds and clinical context, and are usually more current than any single study.
5. The original derivation paper for an equation. For calculators specifically, we always work from the paper that first published the formula, whatever its study design, because that is where the coefficients, the validation sample and the reported error live.
6. Reputable secondary sources. Textbooks, professional-body reference material and established academic health publications, used mainly to check that our reading of a primary source is a mainstream one.

Two deliberate preferences follow from that ordering. We avoid resting a claim on a single small study, however striking its result. Small samples produce large effects that shrink or vanish on replication, and a finding that has not been repeated is preliminary by definition. And we do not treat a press release, a conference abstract or a university media summary as a source; those describe research rather than reporting it, and the gap between the two is where most health misinformation originates. If we cannot reach the paper itself, we do not make the claim.

Where the evidence is genuinely contested, we say so on the page and describe the disagreement instead of picking the side that reads more cleanly. Established consensus, contested evidence and preliminary findings are labelled differently in our guides, because flattening them into a single confident voice would misrepresent what is actually known.

We do not use anecdote, personal testimony, social media claims, supplement or equipment marketing material, or content produced to sell a product as a source for any factual claim. If a claim can only be traced to marketing material, we do not publish it.

How formulas are chosen

Choosing an equation is the single most consequential decision in building a calculator, so it follows a fixed process.

• Find the original. We work from the paper that first published the equation, not from a secondary site's restatement of it. Restatements are where transcription errors breed.
• Check the validation population. Age range, sex, ethnicity, body size and fitness level of the sample the equation was derived from. Where a formula was validated on a narrow group, we say so on the calculator page rather than implying it is universal.
• Prefer the better-validated equation. Where a newer formula has been shown to outperform an older one across more populations, we use it: Mifflin-St Jeor rather than the original Harris-Benedict for resting metabolic rate, Tanaka rather than 220 minus age for heart-rate maximum.
• Show disagreement instead of resolving it. Where several equations are genuinely accepted and give different answers, the calculator runs all of them and displays the spread. Ideal-weight and one-rep-max tools work this way. Presenting a single number would imply a precision that does not exist.

How formulas are verified

Before a calculator is published, its implementation is checked against the source in three ways: worked examples from the original paper are reproduced and must match; results are compared against published reference tables where those exist; and the equation is tested at the edges of its input range to confirm it fails safely rather than returning an absurd figure. Unit conversions between metric and imperial are tested separately, because that is where arithmetic errors most often hide.

Every calculator page carries the equation it uses, written out in full, and a citation to the source it came from. Citations name the authors, the journal, and the volume and year of publication, so the paper can be located rather than merely alluded to; where a stable identifier such as a DOI exists we link to it. Naming the concept without naming the paper (“based on established research”) is not a citation, and we treat it as a defect. If you can see a number on this site, you can see the maths that produced it. That is the whole point of the project, and it is described further on our about page.

Limitations are part of the content

A calculator that reports its result without reporting its error is misleading, even when the arithmetic is correct. So the known limitations of each method appear on the tool itself: that BMI does not distinguish fat from muscle and misclassifies muscular and very tall people; that circumference-based body-fat estimates carry a typical error of three to four percentage points; that activity multipliers in energy calculations are coarse approximations; that obstetric dating by last menstrual period assumes a regular cycle. We put these next to the number, not in the small print underneath.

Review and updates

Calculator pages are reviewed at least once a year, and immediately whenever a relevant guideline changes, a reader reports a problem, or a significant new validation study is published. Guides carry the date they were last reviewed. When we make a substantive change to a formula or a recommendation, we update the review date so you can see how current the page is.

Corrections

We publish corrections rather than quietly deleting mistakes. A substantive correction is anything that changes a number, a recommendation or the meaning of a claim: a wrong coefficient, a bad unit conversion, a misattributed or misread citation, a threshold that does not match current guidance, or a stated limitation that turns out to be incomplete. Those are fixed, noted on the page so the change is visible to anyone who read the earlier version, and acknowledged to whoever reported them. Minor fixes that cannot change how a page is understood, such as typography, grammar, a broken link or a formatting problem, are made without a note, because annotating them would bury the corrections that matter.

To report an error, email jonestitus194@gmail.com or use the contact page. Please include the calculator or guide, the values you entered, and what you believe the correct result should be. Corrections are the messages we prioritise.

Authorship, and what our labels actually mean

Content is produced by the HealthTools editorial team, and guides carry a byline together with their publication date. Where a guide has not been written by a single named individual, it is attributed to the editorial team rather than to an invented persona. We do not publish under fictional author names or fabricated expert profiles, and we do not attach credentials to a byline that the person does not hold.

Two labels appear on guides, and because these are exactly the sort of badge that is routinely overclaimed elsewhere, it is worth stating precisely what ours mean.

• Updated means the page has been revisited since publication and its content changed: a citation refreshed, a threshold corrected against current guidance, or a section rewritten. It is a record of edit history, not a claim of re-verification of every sentence.
• Sources checked (abbreviated to Checked in guide listings) is named for exactly what it is: an editorial accuracy and citation check. It is a second pass confirming that each factual claim traces to the source cited, that the source says what we report it as saying, that equations and thresholds match the original paper or guideline, and that the stated limitations are present and correct. It does not mean the page carries licensed clinical sign-off, and it should not be read as a clinician endorsing the content or vouching for its application to you. If a named, credentialed reviewer ever signs off a page, we will name that person and their credential on the page itself, because an unnamed credential is not evidence of anything.

We would rather carry a label that is narrower than the industry norm and true than one that sounds more reassuring than we can support. Nothing on this site, checked or otherwise, is medical advice; see our medical disclaimer.

Independence from advertising

HealthTools carries advertising, including ads served through Google AdSense, and that advertising is what keeps the site free. Advertising has no influence on editorial content. Specifically:

• No advertiser sees, reviews or approves an article, a calculator, or any statement about a product category before it is published.
• Which formula a calculator uses is decided on the evidence alone. No commercial relationship has ever affected that choice, and none will.
• We do not accept paid product placement, sponsored mentions or paid links in guides. We decline these requests routinely.
• We do not write reviews in exchange for payment or free products.
• No calculator and no guide on this site is sponsored. Not one of them was commissioned, funded or suggested by an advertiser, and we do not offer that arrangement.
• Advertising is served programmatically by third parties, which means we do not choose which individual ads appear. An ad for a diet product, supplement or fitness programme next to our content is not a recommendation, and its presence says nothing about our view of it.
• Ads are labelled as advertising and are kept visually distinct from editorial content so you can always tell which is which.

How advertising cookies work is described in our cookie policy and privacy policy.

What we do not publish

We do not publish diagnostic tools, content that promotes extreme calorie restriction or rapid weight loss, claims that a supplement or device treats a disease, or numeric targets aimed at children. We do not present our calculators as a substitute for clinical assessment. Our medical disclaimer sets out the boundary between health education and medical advice, and we hold to it.

Naming an organisation or study here indicates that we rely on its published work as a source. It does not imply that the organisation endorses, reviews or is affiliated with HealthTools.