How we make sure every calculator is accurate, current, and clearly sourced.
This process is part of our broader commitment to trustworthy health tools, see our About page for the full picture.
How We Build a Calculator
Every calculator starts with a formula, not a design. Before we build anything, we identify the most widely accepted clinical or scientific method for that calculation, drawing from sources like the CDC, WHO, NHLBI, and peer-reviewed journals, rather than a simplified version that's easier to code but less accurate.
Our BMI Calculator, for example, uses the standard weight-to-height-squared formula recognized by the CDC and WHO. Our body fat calculators use validated methods like the U.S. Navy circumference formula rather than rough visual estimates.
Where a topic has more than one accepted method, as with body fat estimation, we choose the one with the strongest evidence behind it and note any real limitations directly on the page rather than glossing over them.
Medical & Scientific Review
Before a calculator goes live, a member of our expert review board reviews it in full. That review covers three things:
The underlying formula and math, checked against the clinical literature it's based on.
The data ranges and category cutoffs used to interpret a result.
The written explanatory content, to confirm it's medically accurate and doesn't overstate what the calculator can actually tell you.
Reviewers are matched to calculators within their own area of expertise. Physicians review clinical measurements like BMI and body surface area, registered dietitians review nutrition-based calculators like TDEE and macros, and exercise physiologists review performance tools like FFMI and one-rep max.
Meet our full Expert Review Board →
Keeping Calculators Current
Clinical guidelines aren't static. Reference ranges get revised, professional bodies update their recommendations, and new research can shift what counts as a healthy range.
Because of that, a calculator is never really "finished." Our expert review board periodically re-checks published calculators against the latest version of the guidelines they're based on, and if something has changed, the formula, its category thresholds, and its written content are all updated and re-reviewed together.
Every calculator page shows the date it was last updated, so you always know how recently it was checked.
Sources & Citations
You shouldn't have to take our word for it. Every calculator lists its sources at the bottom of the page, linking directly to the original research, government health agency, or clinical guideline it's based on. If you want to go deeper than our summary, or verify a claim yourself, the citation is right there.
Errors & Feedback
We work hard to keep every calculator accurate, but if you spot something that looks off, a formula, a category cutoff, or anything in the written content, we want to know. Contact our team with what you found, and we'll review it and correct it as quickly as possible.
This process is what stands behind every result on the site. That said, every calculator remains a general estimate, not medical advice, see our Medical Disclaimer for the full picture.