About PeakCalcs
PeakCalcs is a dedicated health and fitness calculator platform built on a straightforward principle: every estimation tool should be transparent about the formula it uses, where that formula comes from, and what its limitations are. No black boxes, no proprietary algorithms, no hidden assumptions.
Every calculator on PeakCalcs implements formulas drawn exclusively from peer-reviewed scientific literature. The basal metabolic rate tools use the Mifflin-St Jeor equation published in the American Journal of Clinical Nutrition in 1990, the revised Harris-Benedict equation from Roza and Shizgal (1984), and the Katch-McArdle formula for those who know their lean body mass. The one-rep max estimators use the Epley, Brzycki, and Lander formulas — all published in exercise science journals between 1985 and 1993. Body fat estimation draws on the U.S. Navy circumference method (Hodgdon and Friedl, 1999), the Jackson-Pollock skinfold protocols, and the Deurenberg BMI-derived equation.
Who Builds This
PeakCalcs is created and maintained by Dan Dadovic. Dan is a Commercial Director and PhD candidate in IT Sciences based in Northumberland, United Kingdom. His academic and professional background is in computational modelling, data analysis, and web application development — not in medicine, dietetics, or exercise physiology.
That distinction matters. Dan builds precision calculators based on peer-reviewed formulas. He is not a doctor, dietitian, or certified personal trainer. PeakCalcs provides estimation tools, not medical or nutritional advice. The calculators produce estimates grounded in published research, but individual results depend on factors that no formula can fully capture: genetics, medical history, medication, hydration, measurement technique, and more.
Why Multi-Formula Comparison
Most fitness calculator sites pick one formula and present its output as definitive. The problem with this approach is that different formulas were developed for different populations and validated under different conditions. Mifflin-St Jeor tends to be more accurate for the general population, while Katch-McArdle is better calibrated for lean, athletic individuals who know their body fat percentage. Epley and Brzycki produce slightly different one-rep max estimates depending on the rep range used.
PeakCalcs shows results from multiple validated formulas side by side, along with guidance on which formula is most appropriate for a given user profile. This approach gives a more honest picture of the inherent uncertainty in these estimates. A single number on a screen can feel precise; seeing a range across three validated formulas is a better reflection of reality.
Accuracy and Verification
Every calculator undergoes a structured verification process. The implementation is checked against the original publication to ensure the coefficients, units, and operations match. Known-value tests are run using reference inputs and expected outputs derived from the cited source material. Worked examples on each calculator page use real inputs that have been verified against the calculation engine, ensuring the narrative matches the actual output.
This does not make the calculators infallible. Population-level formulas produce population-level estimates. An individual's actual basal metabolic rate, one-rep max, or body fat percentage may differ meaningfully from any formula's prediction. Every calculator page includes a category caveat explaining these limitations, and the Methodology page documents the full verification process.
What PeakCalcs Does Not Do
PeakCalcs does not diagnose medical conditions, prescribe diets, or replace consultation with qualified health professionals. The site does not include clinical or diagnostic tools such as GFR calculators, drug dosage calculators, medical risk scores, or blood panel interpreters. Calorie estimates include hard minimum floors (1,200 kcal/day for women and 1,500 kcal/day for men) and flag any result below these thresholds with a warning that such intake levels require medical supervision.
The pregnancy weight gain calculator uses the Institute of Medicine (IOM) 2009 guidelines and includes enhanced disclaimers directing users to consult their obstetrician, midwife, or healthcare provider. No deficit calculations are available during pregnancy.
Technology and Open Standards
PeakCalcs is built with Next.js, TypeScript, and Tailwind CSS. The site uses structured data (JSON-LD) extensively to ensure search engines and AI systems can accurately understand and reference the tools. Each calculator includes WebApplication, HowTo, and FAQPage schemas. The site provides a machine-readable llms.txt file for AI crawlers, alongside standard sitemap.xml and robots.txt files.
Privacy is handled with explicit consent: Google Analytics 4 only fires after the user actively accepts cookies. No tracking occurs without consent. The full disclosure is available on the Privacy Policy page.
Get in Touch
Questions, feedback, or corrections are welcome. If a formula has been updated, a citation is wrong, or a calculation produces unexpected results, please get in touch. Accuracy matters more than any other feature on this site.
Contact: contact@peakcalcs.com