BMI — body mass index — is a simple way to estimate whether your weight matches your height. Doctors, trainers, and insurance companies use it as a quick initial screening tool.
This is a general reference value, not a diagnosis. For individual interpretation, consult a doctor.
How to calculate BMI
The formula is simple: weight (kg) divided by height squared (m). For example, at 70 kg and 1.75 m: 70 / (1.75 x 1.75) is approximately 22.9.
No need to do the math by hand — the BMI calculator computes it and shows the category right away.
BMI ranges (WHO)
- below 18.5 — underweight
- 18.5-24.9 — normal weight
- 25-29.9 — overweight
- 30 and above — obesity
These thresholds are the same for adult men and women and don't depend directly on age. For children and teens, BMI is assessed differently, using special percentile charts that account for age and sex.
The limits of BMI
BMI doesn't distinguish what your weight is actually made of:
- In athletes with a lot of muscle mass, BMI can show "overweight" even though body fat is low.
- In older adults, who tend to have less muscle, BMI can understate real health risks.
- BMI says nothing about how fat is distributed (for example, abdominal fat is more dangerous than fat elsewhere).
So BMI is a rough first indicator. For a fuller picture, it's also worth looking at waist circumference, body fat percentage, and how you feel.
What to do next
If your BMI is outside the normal range and you want to adjust your weight, start by calculating your daily calorie needs — the calorie calculator shows your maintenance level and options with a deficit or surplus.
BMI is useful precisely because it's simple: a couple of numbers give you a starting point for a conversation about weight.