Question 1

How do you calculate BMI?

Accepted Answer

BMI is calculated by dividing body weight in kilograms by height in meters squared: BMI = Weight (kg) / Height (m)^2. For a person weighing 75 kg at 1.75 m tall: 75 / (1.75 x 1.75) = 24.5.

Question 2

What is a normal BMI?

Accepted Answer

According to the WHO, a BMI between 18.5 and 24.9 is considered normal weight. Values below 18.5 indicate underweight, values from 25 indicate overweight, and from 30 indicate obesity.

Question 3

How meaningful is BMI?

Accepted Answer

BMI is a simple screening value but has limitations: it doesn't distinguish between muscle and fat mass, doesn't account for fat distribution, and doesn't apply to children, pregnant women, or very muscular people. As an initial assessment, it's still useful.

Question 4

Does BMI apply to children?

Accepted Answer

No, for children and adolescents under 18, age- and gender-specific BMI percentiles are used. A child with BMI 22 may be perfectly normal weight, while the same value at a different age may be classified differently.

Question 5

What is the average BMI in Germany?

Accepted Answer

The average BMI in Germany is about 26.7 for men and 25.0 for women (Source: Federal Statistical Office / RKI DEGS1). This means the average falls in the overweight range.

Question 6

At what BMI are you overweight?

Accepted Answer

According to the WHO, overweight starts at a BMI of 25.0 (pre-obese). From BMI 30 it's classified as Obesity Class I, from 35 Class II, and from 40 Class III (morbid obesity).

Question 7

Does the ideal BMI change with age?

Accepted Answer

Yes, some experts recommend slightly higher BMI guidelines for older people. Studies show that a BMI of 25-27 in people over 65 is associated with the lowest mortality. However, WHO categories don't differentiate by age.

Question 8

Why is BMI inaccurate for athletes?

Accepted Answer

Muscle mass is heavier than fat tissue. Muscular athletes can have a BMI over 25 despite low body fat percentage. Better metrics include body fat percentage (via calipers or DEXA scan) or the Ponderal Index.

Question 9

What's the difference between BMI and body fat percentage?

Accepted Answer

BMI is based only on weight and height, while body fat percentage measures the actual fat proportion of total weight. Normal body fat is 10-20% for men and 20-30% for women. Body fat percentage is more meaningful but harder to measure.

Question 10

How often should you calculate your BMI?

Accepted Answer

For healthy adults, calculating BMI every 6-12 months is sufficient. The trend over time is more important than the absolute value. During diet changes or training programs, monthly calculation can be useful.

Guide: BMI Calculator

BMI Calculation and Interpretation: The Complete Guide 2026

BMI Table by Age and Gender: How to Read It Correctly

BMI for Children: Why Percentiles Matter More Than Fixed Values

BMI Alternatives: Waist-to-Hip Ratio, Body Fat Percentage and More

Ideal Weight Calculation: 5 Methods Compared

BMI for Athletes: Why Muscle Mass Skews the Results