Health & Fitness
BMI Calculator
Calculate body mass index from height and weight, and see the healthy weight range for your height.
Updated 20 Sep 2026
A BMI of 22.9 falls in the "Healthy weight" range. For your height, the healthy-weight band is roughly 56.7–76.3 kg. BMI is a population screening measure, not a diagnosis — it does not account for muscle mass, body composition, age or ethnicity.
Enter your weight in kilograms and height in centimetres. The calculator returns your BMI, the WHO category it falls into, and the weight range that would put you in the healthy band for your height.
What is the BMI Calculator?
Body mass index is weight in kilograms divided by height in metres squared. It was designed in the nineteenth century to describe populations, not individuals, and that origin matters when interpreting it.
BMI is a rough screening tool. It says nothing about body composition, fat distribution, muscle mass or fitness.
How to use the BMI Calculator
- Enter your weight in kilograms.
- Enter your height in centimetres.
The result appears immediately, along with the healthy weight range for your height.
Formula
WHO adult categories:
Under 18.5 Underweight
18.5 to 24.9 Healthy weight
25.0 to 29.9 Overweight
30.0 and above Obese
Height must be in metres, so a height entered in centimetres is divided by 100 first. Someone 175 cm tall has a height of 1.75 m, and 1.75² = 3.0625.
How the calculation works
Dividing weight by height squared adjusts for the fact that taller people are naturally heavier. The square is an approximation — human bodies do not scale perfectly with the square of height, which is part of why BMI systematically misclassifies very tall and very short people.
Worked example
Someone weighing 70 kg at 175 cm:
- Height in metres = 1.75
- Height squared = 3.0625
- BMI = 70 ÷ 3.0625 = 22.9
That falls in the healthy range. For this height, the healthy band spans roughly 56.7 kg to 76.3 kg.
Uses and benefits
- A quick reference point to discuss with a doctor.
- See the healthy weight range for your height rather than a single target number.
- Track a rough trend over time alongside more meaningful measures.
Frequently asked questions
The WHO defines 18.5 to 24.9 as the healthy range for adults. Below 18.5 is classed as underweight, 25 to 29.9 as overweight and 30 or above as obese. Some health authorities use lower thresholds for South Asian populations.
No. It cannot distinguish muscle from fat, so it classifies many athletes as overweight. It is also unreliable for older adults, children, pregnant women and anyone at the extremes of height. It is a population screening measure, not an individual diagnosis.
Treat it as one data point and speak to a doctor. Waist circumference, blood pressure, blood glucose and lipid profile all tell you more about actual health risk than BMI alone.
References
Categories follow the World Health Organization classification for adults. BMI does not distinguish muscle from fat, and it misclassifies athletes, older adults with reduced muscle mass, and pregnant women. Some health bodies apply lower thresholds for South Asian populations, where cardiometabolic risk rises at lower BMI values. This tool is not a diagnosis — discuss any concerns with a doctor.