About CalculateMyBMI.net
Free, evidence-based BMI and body composition calculators. Built and maintained by Marko Visic, MPharm, and operated by Moving Data Systems d.o.o.
Marko Visic, MPharm
Marko is a pharmacist by training. He holds a Master of Pharmacy (MPharm) from the Faculty of Pharmacy, University of Ljubljana, Slovenia, and a BSc in Physics from the University of Ljubljana. He builds evidence-based health calculators and writes the guides on this site. CalculateMyBMI.net is operated by Moving Data Systems d.o.o., based in Maribor, Slovenia. Marko is not a physician; nothing on this site is personal medical advice.
Contact: info@calculatemybmi.net · LinkedIn
About the site
CalculateMyBMI.net exists to make BMI and body-composition screening tools available for free, without account creation or invasive data collection. Body Mass Index is recommended by the World Health Organization (WHO), the Centers for Disease Control and Prevention (CDC), and the National Heart, Lung, and Blood Institute (NHLBI) as a first-line screening metric — but many people have never calculated their BMI or seen it interpreted in context.
The site provides a suite of calculators that goes beyond a single number: results are shown alongside plain-language interpretation drawn from published medical guidance. Alongside the standard BMI calculator, there are calculators for women, men, age-adjusted, and children, plus ideal weight, lean body mass, and the Trefethen height-corrected BMI variant.
Why it exists
The site aims to (1) make BMI and body-composition screening tools freely accessible, (2) explain what BMI and related metrics actually mean through the guides section (starting with the what-is-BMI guide), and (3) help readers prepare more informed conversations with their own healthcare providers. It is not a substitute for a clinician.
Free Forever
No registration, no hidden costs, no premium tiers. Every calculator is free for everyone.
Evidence-Based
All formulas are sourced from peer-reviewed research and established clinical standards.
Accessible to All
Simple, intuitive interfaces with support for both metric and imperial unit systems.
Health inputs stay local
All calculator inputs are processed in your browser and never reach our servers. See the privacy policy for what we do collect (Google Analytics 4 cookies and standard server logs).
Calculators on the site
Eight calculators cover different aspects of body-composition and weight screening. See the calculators index for all of them, or the BMI categories guide for how the numbers are classified.
Standard BMI Calculator
Calculate your Body Mass Index using the universally recognized WHO formula. Enter your height and weight to receive an instant BMI classification with a detailed breakdown of what your result means for your health.
BMI Calculator for Women
A BMI calculator with female-specific interpretation and context. Accounts for the fact that women naturally carry a higher percentage of body fat than men, and provides guidance across life stages including pregnancy and menopause.
BMI Calculator for Men
Tailored for male physiology with considerations for muscle mass and body composition differences. Includes context on how higher muscle density can affect BMI readings and guidance for athletic body types.
BMI by Age Calculator
Age-adjusted BMI interpretation that accounts for how healthy weight ranges shift across decades. Provides decade-specific guidance from young adults through older age, reflecting the latest research on age and body weight.
Pediatric BMI Calculator
Uses CDC growth chart percentiles to assess BMI for children and teens ages 2 through 19. Results are presented as age- and sex-specific percentile rankings rather than fixed adult categories, following pediatric clinical guidelines.
New BMI Calculator (Trefethen)
Implements the height-corrected BMI formula proposed by Oxford mathematician Nick Trefethen in 2013. This formula addresses the known limitation of the traditional BMI equation that overestimates BMI for tall individuals and underestimates it for shorter people.
Ideal Weight Calculator
Calculates your ideal body weight using four established clinical formulas: Devine (1974), Robinson (1983), Miller (1983), and Hamwi (1964). Compare results across all four methods for a comprehensive perspective on your target weight range.
Lean Body Mass Calculator
Estimates your lean body mass (total weight minus fat weight) using the Boer, James, and Hume formulas. Essential for understanding body composition beyond what BMI alone can reveal, particularly useful for fitness tracking and nutritional planning.
Methodology
Every calculator on CalculateMyBMI.net implements a peer-reviewed formula or classification system used in clinical practice. Nothing on this site is an original method; the tools implement equations that have been in the medical literature for years or decades.
Formulas and standards implemented
- Standard BMI Formula: BMI = weight (kg) / height (m)², established by Adolphe Quetelet and adopted globally by the WHO for population-level weight screening since the 1990s.
- WHO BMI Classification: Underweight (<18.5), Normal (18.5–24.9), Overweight (25.0–29.9), Obese Class I (30.0–34.9), Obese Class II (35.0–39.9), and Obese Class III (≥40.0).
- CDC Growth Charts: For pediatric BMI calculations, we use the CDC's 2000 sex-specific BMI-for-age percentile growth charts, which classify children as underweight (<5th percentile), healthy weight (5th–84th), overweight (85th–94th), or obese (≥95th percentile).
- Trefethen BMI Formula: New BMI = 1.3 × weight (kg) / height (m)^2.5, as proposed by Professor Nick Trefethen of the University of Oxford in 2013, which corrects for height bias in the traditional formula.
- Ideal Weight Formulas: Devine (1974), Robinson (1983), Miller (1983), and Hamwi (1964) equations, each originally developed for clinical dosing and nutritional assessments and now widely used in healthcare settings.
- Lean Body Mass Formulas: Boer (1984), James (1976), and Hume (1966) equations, developed from clinical studies measuring body composition through established anthropometric methods.
Organisations referenced across the site
This is not a global citation list — each guide and calculator page carries its own inline references. The following organisations are the ones most often linked to for classification standards, clinical thresholds, and background context:
Content is updated when authoritative bodies revise their guidance (for example WHO or CDC classification changes) and when specific pages are revisited. See the guides for the full library and the BMI categories guide for the classification detail.
How the calculators work
Client-side processing
All calculation runs in your browser via client-side JavaScript. Height, weight, age, and sex inputs are processed on your device and are not transmitted to the server. What the site does collect (Google Analytics 4 cookies, standard HTTP server logs) is described in the privacy policy.
Instant results
Because processing is local, results appear immediately after you click Calculate — no server round-trip, no wait.
No account required
No email address, no sign-up, no cookie wall. Load a page, use the tool.
Imperial and metric
Every calculator supports both imperial (pounds, feet, inches) and metric (kilograms, centimetres). Toggling between them converts inputs automatically.
Editorial approach
Sourcing
Every quantitative claim on the site is either linked to an institutional source (WHO, CDC, NHLBI, NIH, ACOG, Mayo Clinic, Harvard Health) or a specific paper (Flegal 2013, Winter 2014, Trefethen 2013, and the ideal-weight and lean-body-mass equations by their original authors). Where a claim cannot be sourced, it is left off the page rather than hedged.
Scope
The site covers what BMI is, how it is calculated, what the WHO categories mean, how they should be read for children, older adults, athletes, and pregnancy, and what BMI does not capture. It does not cover medical treatment content — medication choices, bariatric surgery decisions, or clinical diagnostic thresholds. Those belong with a qualified clinician.
Updates
Pages are updated when authoritative bodies revise their guidance and when individual pages are revisited.
Medical disclaimer
The calculators and content on CalculateMyBMI.net are provided for informational and educational purposes only. They are not a substitute for professional medical advice, diagnosis, or treatment. BMI is a screening tool, not a diagnostic measure. It does not account for muscle mass, bone density, ethnic differences, or individual health conditions. Consult a qualified healthcare provider before making decisions about your health, diet, or exercise based on your BMI or any other metric.
Why BMI matters
Despite its limitations, BMI remains one of the most widely used weight screening tools. It is:
- Universally recognised: BMI is used by the WHO, CDC, NHS, and virtually every public health organisation as a first-line screening tool for weight-related health risks.
- Simple and accessible: It needs only two measurements — height and weight — which makes it practical in clinical settings, population studies, and self-tracking alike.
- Extensively studied: Decades of epidemiological research have documented associations between BMI ranges and outcomes including cardiovascular disease, type 2 diabetes, and certain cancers.
- A screening prompt, not a diagnosis: A BMI outside the healthy range is a prompt for further evaluation — body-fat percentage, waist circumference, blood panels — not a diagnosis in itself.
- Free and immediate: Unlike blood tests, DEXA scans, or clinical evaluations, BMI can be calculated instantly at no cost.
Read BMI as one piece of a larger health picture. Consider it alongside a lean body mass estimate and an ideal weight target range, and take the results to your own healthcare provider for interpretation. Deeper detail is in the guides section, particularly BMI limitations, body fat vs BMI, and BMI for athletes.
Privacy
Health-related data is sensitive. The site is designed so calculator inputs never leave your browser. Full detail is in the privacy policy; the rules of use are in the terms of service.
Calculator inputs stay local
Your height, weight, age, and BMI results are processed in your browser and are not sent to our servers or stored in any database.
Client-side calculation
All arithmetic runs in JavaScript on your device. The specific inputs you type into a calculator are not transmitted from your device.
GDPR & CCPA rights honoured
We follow GDPR and CCPA / CPRA. Rights and how to exercise them are in the privacy policy.
What we do collect
Google Analytics 4 cookies (with consent for EEA/UK/CH visitors) and standard HTTP server logs. Full detail: privacy policy.
Two things happen to data on the site: calculator inputs are processed in your browser and are not transmitted from your device, and standard analytics/server-log processing runs as described in the privacy policy. The site does not currently serve advertisements.
Frequently asked questions
The calculators implement the same formulas used in clinical practice: the standard BMI formula (weight in kilograms divided by height in metres squared), the CDC growth-chart percentile method for children, the Trefethen height-corrected variant, the Devine/Robinson/Miller/Hamwi ideal-weight equations, and the Boer/James/Hume lean-body-mass equations. BMI is a screening tool with known limitations — it does not distinguish muscle from fat mass, and results should be interpreted alongside guidance from a healthcare professional.
Calculator inputs (height, weight, age, sex) are processed in your browser and are not transmitted to the server or to any third party. There is no database of your inputs, and no cookie records what you typed into a calculator. Separately, the site does set Google Analytics 4 cookies (page-view counting) and produces standard HTTP server logs — see the privacy policy for the full picture.
The site is built and maintained by Marko Visic, MPharm, and operated by Moving Data Systems d.o.o. The calculators implement formulas from peer-reviewed literature (Devine, Robinson, Miller, Hamwi for ideal weight; Boer, James, Hume for lean body mass; the Quetelet formula for BMI; Trefethen 2013 for the height-corrected variant) and reference institutional guidance from WHO, CDC, NHLBI, and other bodies. No original methodology is introduced — the site presents established science.
The calculators are informational and educational. They use the same formulas that appear in clinical practice, but the results are not a substitute for professional medical evaluation. BMI is one of many things a healthcare provider considers when assessing health. Take your result to a doctor, nutritionist, or other qualified professional who can interpret it against your full medical history and any relevant labs.
Pages are updated when authoritative bodies revise their guidance (for example, a WHO or CDC classification change) and when individual pages are revisited.
No. All calculators are free to use with no registration. No email address, no username, no sign-up. Load a page and start using it.
Eight calculators covering different population and use cases (women, men, age-adjusted, pediatric, Trefethen height-corrected, ideal weight, lean body mass), rather than one generic tool. Each carries context-specific interpretation, supports both imperial and metric units, runs entirely in your browser, and links to the institutional guidance behind the numbers. The guides section explains the underlying science, the limitations of BMI, and how to read your result alongside other health metrics.
Contact
Corrections, suggestions, and feedback are welcome — particularly if you spot a factual error in a guide or a calculator result that looks wrong.