Why we built this.
The "drink 8 glasses a day" rule has been cited for decades — but a 2002 review published in the American Journal of Physiology found no specific scientific basis for it. Real hydration needs vary considerably based on body weight, age, activity level, climate, and individual health status.
Our goal is to provide a personalized, evidence-informed starting point — not a replacement for professional guidance, but a better-than-generic number that respects the complexity of individual biology. Every calculation is an estimate. We say so clearly, on every page.
About the editorial team.
waterintakecalci.com is maintained by a small editorial team with backgrounds in health communication, web development, and science writing. We are not a medical practice. We do not employ physicians as staff authors.
Our role is to translate published, peer-reviewed health guidance into accessible, original language — with appropriate hedging, clear attribution to source organisations, and prominent reminders that individual needs vary and professional consultation matters.
Note: We are a health information resource, not a medical provider. Nothing on this Site constitutes medical advice. See our full Medical Disclaimer.
Our editorial process.
Every piece of content on this Site follows the same process before publication:
Identify the topic and research question
We start with a clearly defined question a real user might have — "How much water should I drink a day?" rather than vague lifestyle topics.
Gather primary sources
We consult guidelines from WHO, the National Academies of Sciences, EFSA, ACSM, NHS, and CDC, as well as peer-reviewed systematic reviews and meta-analyses where available.
Assess evidence quality
We distinguish between strong consensus, emerging evidence, and limited research. Where evidence is mixed or uncertain, we say so explicitly rather than overstating conclusions.
Write original content
We write entirely original text — never copying from source organisations. All health claims use appropriately hedged language ("research suggests," "evidence indicates," "for many healthy adults").
Review for medical language compliance
Before publication, every page is reviewed against our medical content rules: no absolute claims, no promises of outcomes, no diagnosis or treatment language, no unsupported statements.
Add citations and disclaimers
Every health-related page includes a references section identifying the organisations and studies that informed the content, plus a visible medical disclaimer.
Schedule for review
All content is marked with a publication date. High-traffic pages are reviewed annually or whenever major guideline updates are published.
How we research.
Our source hierarchy, from highest to lowest preference:
Systematic reviews & meta-analyses
The highest level of evidence — synthesising results across multiple studies to identify consistent patterns.
Randomised controlled trials (RCTs)
Gold-standard individual study design for establishing causation.
Official guidelines from major health bodies
WHO, National Academies, EFSA, ACSM, NHS, CDC — organisations that synthesise evidence to produce consensus recommendations.
Observational cohort studies
Useful for understanding associations, but we note these cannot prove causation.
Expert consensus statements
Used when controlled evidence is limited, with explicit disclosure of evidence level.
We do not accept content based solely on anecdote, influencer claims, or marketing material. When the best available evidence is limited or contradictory, we say so.
Scientific foundations and sources we use.
The calculator formula and educational content are informed by the following organisations and publications:
National Academies of Sciences (formerly Institute of Medicine)
Dietary Reference Intakes for Water (2004) — sets adequate intake benchmarks of 3.7 L/day total fluid for men and 2.7 L/day for women as a population-level starting point.
World Health Organization (WHO)
Hydration, drinking-water quality, and climate-related fluid adjustment guidance used in public health contexts globally.
American College of Sports Medicine (ACSM)
Exercise and Fluid Replacement Position Stand — the primary basis for exercise-adjusted fluid calculations, recommending approximately 500ml per 30 minutes of exercise.
European Food Safety Authority (EFSA)
Scientific Opinion on Dietary Reference Values for Water (2010) — sets adequate water intake at 2.0 L/day for adult women and 2.5 L/day for adult men from beverages alone.
NHS (UK National Health Service)
Practical hydration guidance for the general population, referenced for UK-audience relevance.
Valtin H. (Am J Physiology, 2002)
Peer-reviewed analysis questioning the scientific basis of the "8×8 glasses per day" rule — foundational to our critique of one-size-fits-all hydration advice.
Popkin BM et al. (Nutrition Reviews, 2010)
Comprehensive review of water, hydration, and health — covering benefits of adequate hydration across physiological systems.
Content update policy.
Health and nutrition science evolves. We are committed to keeping our content current:
- High-traffic pages (homepage, how-much-water, signs of dehydration) are reviewed at minimum annually.
- If a major health organisation updates a relevant guideline, we update the affected content within 30 days.
- All pages display a "Last updated" date so you can assess currency.
- Factual corrections are made promptly and noted in the content when significant.
Conflicts of interest.
waterintakecalci.com is supported by display advertising (Google AdSense). We do not accept sponsored content, paid product placements, or affiliate arrangements that would influence our editorial content. Advertisements are clearly separate from editorial content. We do not receive payment from any health organisation, supplement brand, or beverage company for content placement.
Privacy and data architecture.
All hydration tracking data is stored locally in your browser's localStorage. We do not collect, store, or transmit the personal data you enter into the calculator (weight, age, etc.). We use Google Analytics for anonymous site traffic analysis and Google AdSense for advertising. Full details are in our Privacy Policy.