How we research, build, and maintain trustworthy health tools and content.
HealthCheck provides health and fitness calculators that millions of people depend on to make decisions about their wellbeing. We take that responsibility seriously. Every calculator formula, every piece of educational content, and every recommendation on this site goes through a structured process designed to ensure it is accurate, current, and backed by credible science.
Health content is classified as "Your Money or Your Life" (YMYL) by major search engines because it can directly affect a person's health and safety. That classification drives our editorial standards: we hold ourselves to the same rigor you would expect from a clinical reference, while keeping the language accessible to everyone.
Every calculator on HealthCheck is built on a specific, published formula chosen for its accuracy and clinical acceptance. Here is a quick reference of which formula powers each major tool:
| Calculator | Primary Formula | Source |
|---|---|---|
| BMI | WHO Classification + CDC Growth Charts | WHO, 2000 / CDC |
| TDEE / BMR | Mifflin-St Jeor (default), Harris-Benedict, Katch-McArdle | Am J Clin Nutr, 1990 |
| Body Fat | U.S. Navy Method + BMI-based estimation | Hodgdon & Beckett, 1984 |
| Calorie Deficit | Mifflin-St Jeor BMR with activity multipliers | Am J Clin Nutr, 1990 |
| Heart Rate Zones | 220-age method + Karvonen formula | ACSM Guidelines, 2021 |
| ABSI | A Body Shape Index | Krakauer & Krakauer, 2012 |
| Waist-to-Hip Ratio | WHO waist-to-hip ratio classification | WHO, 2008 |
When more than one formula is available for a calculation, we present them all and explain the trade-offs so you can make an informed choice. Detailed descriptions of each formula appear further down this page.
Content review at HealthCheck is not a one-time event. It is a continuous cycle that ensures our tools and articles stay accurate as science progresses. Our review process covers three distinct areas:
Every calculator is tested against published reference values. Our automated test suite runs 1,300+ tests across all calculators to catch regressions and edge cases.
Blog posts and calculator explanations are checked against current clinical guidelines. We update articles when new research changes established recommendations.
Product recommendations are updated when items are discontinued, pricing changes materially, or a significantly better option enters the market.
Each piece of reviewed content shows a "Last reviewed" date. If you believe something needs updating, please let us know.
All content on HealthCheck starts with a review of the current scientific literature. We draw from peer-reviewed journals, clinical guidelines, and established textbooks in exercise science, nutrition, and public health. We do not rely on anecdotal claims or unverified sources.
When multiple valid approaches exist for a given calculation, we present them transparently and explain the trade-offs. For example, our body fat calculator offers both the U.S. Navy method and the BMI-based estimation so users can compare and understand the limitations of each approach.
Our calculators are built on formulas that have been validated in controlled research settings. Here are some of the key methodologies we use:
Published in 1990, this equation is considered the most accurate for estimating basal metabolic rate in healthy adults. The American Dietetic Association recommends it as the preferred formula for clinical use. We use it as the default in our TDEE, calorie deficit, and weight management calculators.
One of the oldest and most widely cited BMR formulas, originally published in 1919 and revised in 1984 by Roza and Shizgal. We offer it as an alternative in our TDEE calculator for users who want to compare results across methodologies.
This formula accounts for lean body mass, making it more accurate for people who know their body fat percentage. It is especially useful for athletes and those with above-average muscle mass.
Developed by Hodgdon and Beckett at the Naval Health Research Center, this circumference-based method provides a practical estimate of body fat percentage without specialized equipment. It correlates well with hydrostatic weighing in most populations.
Our BMI calculator follows the World Health Organization classification system for adults and uses CDC growth chart percentiles for children and adolescents, providing age- and sex-appropriate assessments.
Developed by Krakauer and Krakauer (2012), ABSI accounts for waist circumference relative to BMI and height. Research has shown it to be a stronger predictor of mortality risk than BMI alone, particularly for identifying abdominal obesity risk.
We support both the standard age-predicted maximum heart rate method (220 minus age) and the Karvonen formula, which factors in resting heart rate for more personalized training zone calculations used by the ACSM.
Every piece of content goes through a multi-step review before publication:
Content is drafted with references to primary scientific sources. Calculator formulas are implemented directly from published research papers.
Calculator outputs are tested against known reference values from published studies. Our test suite runs over 850 automated tests to verify calculation accuracy across edge cases and different input ranges.
Content is reviewed by health and fitness professionals with credentials in exercise science, nutrition, or related clinical fields. Reviewers check for factual accuracy, appropriate disclaimers, and clarity.
After publication, we monitor for user feedback, new research, and updated clinical guidelines that might require content revisions.
Health science evolves, and so does our content. We review our calculators and educational articles on a regular basis:
We believe in transparency about where our information comes from. When we cite a specific statistic, formula, or clinical recommendation, we reference the original source. Here are some of the key references that underpin our calculators:
We are honest about what our tools can and cannot do. Online health calculators are useful screening and educational tools, but they have inherent limitations:
We encourage all users to discuss calculator results with their doctor, dietitian, or certified fitness professional, especially when making significant changes to their diet or exercise routine.
The information and tools provided on HealthCheck are for educational and informational purposes only. They are not intended to be a substitute for professional medical advice, diagnosis, or treatment.
Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay seeking it because of something you have read or calculated on this website.
Our calculators use established scientific formulas to provide estimates, but individual results may vary. Factors such as medical conditions, medications, and genetics can affect accuracy.
We welcome feedback from users, healthcare professionals, and researchers. If you believe any of our content contains an error, or if you have suggestions for improvement, please reach out.