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Wat is BMI?
De Body Mass Index (BMI) is een eenvoudige screeningsmaat die lichaamsvet schat op basis van het gewicht en de lengte van een persoon. Ontwikkeld door de Belgische wiskundige Adolphe Quetelet in de jaren 1830, is BMI het meest gebruikte hulpmiddel om individuen te classificeren als ondergewicht, normaal gewicht, overgewicht of obees.
Hoewel BMI niet direct lichaamsvet meet of rekening houdt met spiermassa, botdichtheid of vetverdeling, biedt het een snel en nuttig uitgangspunt voor het beoordelen van gewichtsgerelateerde gezondheidsrisico's.
How BMI is Calculated
The BMI formula divides weight by the square of height. The result is a single number that maps to standard health categories.
- Metric formula — BMI = weight (kg) / height (m) squared. For example, 70 kg and 1.75 m gives BMI = 70 / (1.75 x 1.75) = 22.9
- Imperial formula — BMI = (weight in pounds x 703) / height in inches squared. For example, 154 lbs and 69 inches gives BMI = (154 x 703) / (69 x 69) = 22.7
- Both formulas produce the same result — the calculator handles unit conversion automatically when you toggle between metric and imperial
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Bereken je BMI →BMI Categories
The World Health Organization defines four main BMI categories based on statistical health risk associations.
- Underweight (BMI < 18.5) — may indicate malnutrition, eating disorders, or other health conditions requiring medical attention
- Normal weight (BMI 18.5 – 24.9) — associated with the lowest statistical risk of weight-related health problems
- Overweight (BMI 25.0 – 29.9) — associated with increased risk of cardiovascular disease, type 2 diabetes, and other conditions
- Obese (BMI 30.0 and above) — associated with significantly elevated health risks; further subdivided into classes I, II, and III
Limitations & Context
BMI is a useful screening tool but has important limitations to understand.
- Does not distinguish muscle from fat — athletes and bodybuilders often have 'overweight' BMI despite low body fat percentage
- Does not account for fat distribution — abdominal fat carries higher health risks than fat in other areas, but BMI does not differentiate
- Age and sex considerations — BMI categories were developed primarily for adults; children and elderly individuals may need adjusted scales
Frequently Asked Questions
Is BMI accurate for athletes?
BMI can be misleading for athletes and people with high muscle mass. Since muscle weighs more than fat per unit volume, muscular individuals often show an 'overweight' BMI despite having healthy or low body fat. For athletes, body fat percentage or waist-to-hip ratio may be more informative.
What BMI is considered healthy?
A BMI between 18.5 and 24.9 is considered normal weight by WHO standards. However, optimal BMI varies by age, sex, ethnicity, and individual health factors. BMI should be one of several metrics considered — not the sole indicator of health.
Should I use metric or imperial for more accurate results?
Both systems produce identical BMI values when calculated correctly. Use whichever measurement system you're most comfortable with. The calculator handles the math regardless of your preferred units.