BMI Calculator
What BMI measures, what it misses, and the calculators to work it out properly - including the ones that answer better questions than BMI does.
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When BMI Reads Wrong: Populations for Whom Standard BMI Misclassifies Health Risk
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BMI Calculator: Understand Your Body Mass Index Number and Its Limits
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TDEE Calculator: Estimate Your Total Daily Energy Expenditure as a Range
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Body Fat Calculator: US Navy Method Estimate and Its Error Against DXA
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Ideal Weight Calculator: See the WHO Healthy BMI Range for Your Height
Guides by category
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BMI and health risk
BMI is associated with mortality and disease risk at the population level, but the relationship is shaped by confounding, reverse causation, and body composition differences.
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Body composition
BMI measures weight-for-height, not body composition. This hub routes you to guides on waist-to-height ratio, body fat percentage, visceral fat, and muscle mass, with every threshold attributed to its source.
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Children and teenagers
How to understand a child's BMI result, growth chart position, and what it means for health, with every threshold attributed to its issuing body and year.
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Measuring it properly
Self-reported numbers produce a BMI roughly 0.5-1.5 kg/m² lower than measured ones. These guides give you the protocol to close that gap, with the error size named for each step.
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The calculators
Route to the right body measurement calculator by what you are trying to understand, with every equation's source and margin of error stated before you enter a number.
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Understanding BMI
Understanding body mass index: a hub routing you to guides on BMI screening, measurement methods, population thresholds, and what BMI can and cannot tell you.
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Weight and energy balance
How basal metabolic rate, total daily energy expenditure, calorie deficit and metabolic adaptation interact—explained through mechanisms, not prescriptions.
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When BMI reads wrong
Which populations standard BMI misclassifies—athletes, older adults, pregnant women, and ethnic groups—and what measurements are used instead, with every threshold sourced.
Latest articles
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Waist to Height Ratio Calculator: Measure Central Adiposity Risk at Home
Calculate your waist-to-height ratio and learn why NICE CG189 uses the 0.5 boundary, how to measure consistently, and how the WHO and NIH landmarks differ.
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Child BMI Calculator: Plot Your Child's Percentile on CDC Growth Charts
Calculate your child's BMI percentile using CDC 2000 growth charts and understand what a centile actually means—and why it is not a body fat measurement.
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Body Composition Beyond BMI: Waist, Body Fat and Visceral Fat Guides
BMI measures weight-for-height, not body composition. This hub routes you to guides on waist-to-height ratio, body fat percentage, visceral fat, and muscle mass, with every threshold attributed to its source.
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BMI and Health Risk: What the Number Does and Does Not Predict
BMI is associated with mortality and disease risk at the population level, but the relationship is shaped by confounding, reverse causation, and body composition differences.
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Children and Teenagers BMI, Growth Charts and Percentiles Hub
How to understand a child's BMI result, growth chart position, and what it means for health, with every threshold attributed to its issuing body and year.
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Measuring Body Weight, Height, and Composition: A Guide to Getting Numbers That Mean Something
Self-reported numbers produce a BMI roughly 0.5-1.5 kg/m² lower than measured ones. These guides give you the protocol to close that gap, with the error size named for each step.
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Body Measurement Calculators: BMI, TDEE, Body Fat, and Waist Ratio Tools Explained
Route to the right body measurement calculator by what you are trying to understand, with every equation's source and margin of error stated before you enter a number.
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BMI Explained: What Body Mass Index Actually Measures and What It Misses
Body mass index explained: the formula, the WHO cut-offs from 1995, what BMI measures at population scale, and what it cannot tell any single person about their health.
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Understanding BMI: A Guide to Body Mass Index Screening and Its Limits
Understanding body mass index: a hub routing you to guides on BMI screening, measurement methods, population thresholds, and what BMI can and cannot tell you.