BMI Calculator (Body Mass Index)
Healthy weight table by your height
Move the slider to see weight for each WHO category.
| WHO category | IMC | Weight range |
|---|---|---|
| Underweight | < 18.5 | up to 53.5 kg |
| Normal weight | 18.5 – 24.9 | 53.5 – 72.0 kg |
| Overweight | 25.0 – 29.9 | 72.3 – 86.4 kg |
| Obesity I | 30.0 – 34.9 | 86.7 – 100.9 kg |
| Obesity II | 35.0 – 39.9 | 101.1 – 115.3 kg |
| Obesity III | ≥ 40.0 | from 115.6 kg |
BMI, or Body Mass Index, is the most widely used indicator in the world to assess whether your weight falls within a healthy range for your height. It was defined by Adolphe Quetelet in 1832 and adopted by the World Health Organization as a global standard in 1997. With this calculator, enter your weight in kilograms and your height in centimeters, and you'll instantly get your BMI, the WHO category (underweight, normal, overweight, or obesity grades I, II, or III), and the healthy weight range for your height. It works for adults between 18 and 65 years old, requires no registration, and the calculation runs entirely in your browser — your data never leaves your device.
When to use this calculator
- You want to know if your current weight falls within the healthy range recommended by the WHO.
- You're about to start a diet and want an objective baseline.
- You had a medical checkup and want to understand what the BMI in your report means.
- You go to the gym and want a baseline number to track your progress over time.
- You're a parent and want to understand how weight is assessed during medical consultations.
Example: Woman, 1.65 m and 68 kg
- Data: weight = 68 kg, height = 1.65 m.
- Formula: BMI = weight / height² =
68 / (1.65 × 1.65)=68 / 2.7225. - Result: BMI = 24.98.
- WHO Category: Normal weight (range 18.5 – 24.9), at the upper boundary.
- Healthy weight range for 1.65 m: between 50.4 kg and 67.8 kg.
How it works
2 min readWhat Is BMI?
The Body Mass Index (BMI) is a formula created in 1832 by Belgian mathematician Adolphe Quetelet and adopted by the World Health Organization (WHO) in 1997 as the most widely used global indicator of nutritional status in adults. Today, doctors, nutritionists, and health organizations worldwide use it to quickly assess whether a person is within a healthy weight range.
How BMI Is Calculated
BMI = weight (kg) / height² (m)Weight is in kilograms and height is in meters, squared. If you measure height in centimeters, divide by 100 first: 170 cm = 1.70 m.
WHO Category Table
| BMI | Category | Risk |
|---|---|---|
| < 18.5 | Underweight | Increased |
| 18.5 – 24.9 | Normal weight ✅ | Low |
| 25.0 – 29.9 | Overweight | Increased |
| 30.0 – 34.9 | Obesity grade I | Moderate |
| 35.0 – 39.9 | Obesity grade II | High |
| ≥ 40.0 | Obesity grade III (morbid) | Very high |
Healthy Weight by Height (Approximate)
| Height | Min Weight | Max Weight |
|---|---|---|
| 1.50 m | 41.6 kg | 56.0 kg |
| 1.55 m | 44.4 kg | 59.8 kg |
| 1.60 m | 47.4 kg | 63.7 kg |
| 1.65 m | 50.4 kg | 67.8 kg |
| 1.70 m | 53.5 kg | 71.9 kg |
| 1.75 m | 56.6 kg | 76.2 kg |
| 1.80 m | 59.9 kg | 80.6 kg |
| 1.85 m | 63.3 kg | 85.2 kg |
| 1.90 m | 66.8 kg | 89.9 kg |
When BMI Doesn't Work Well
Common Mistakes When Calculating BMI
1. Using height in centimeters: classic error. 170 cm² is not 1.70 m². Always convert to meters.
2. Weighing at different times: weight can vary 1–2 kg between morning and night. Weigh yourself fasting and always at the same time.
3. Treating it as a diagnosis: BMI is a signal, not a diagnosis. Add body fat percentage, waist circumference, and blood tests for a full picture.
4. Comparing BMI between people: two individuals with the same BMI can have very different body compositions.
Beyond BMI: Useful Complements
For a complete assessment, consult a registered dietitian or physician. BMI is a good starting point, not the final picture.
Frequently asked questions
What is a healthy BMI?
According to the WHO, a healthy BMI for adults is between 18.5 and 24.9. Below that is considered underweight, and above it is overweight. Starting at 30, you enter obesity in its various grades (I, II, and III).
Is BMI the same for men and women?
Yes. The WHO uses the same range (18.5 – 24.9) for both sexes in adults. The difference in body composition between men and women is assessed with other indicators like body fat percentage.
How much should I weigh for my height?
Multiply your height in meters squared by 18.5 (minimum weight) and by 24.9 (maximum weight). For example, for 1.70 m: minimum 53.5 kg, maximum 72 kg. The calculator shows this automatically.
How much can my BMI vary in a day?
Very little in BMI terms, because daily weight varies 1–2 kg (due to fluids and food). But if you weigh yourself at the same time (ideally fasting), your BMI is stable. For tracking, the important thing is the weekly or monthly trend.
Why can an athlete have a high BMI without being overweight?
Because muscle weighs more than fat. BMI doesn't distinguish between muscle mass and fat mass. Rugby players, bodybuilders, and powerlifters often score 'overweight' or 'obese' on BMI but have a low body fat percentage. For them, body fat percentage is a much more useful indicator.
Does BMI work for people over 65?
The WHO suggests expanding the healthy range to 23 – 28 for those over 65 because maintaining slightly more weight protects against sarcopenia (age-related muscle loss). A very low BMI in older adults is associated with higher mortality.
What are the limitations of BMI as a health indicator?
BMI does not account for body composition (muscle vs. fat), fat distribution (visceral vs. subcutaneous), age, ethnicity, or fitness level. Two people with identical BMIs can have vastly different health profiles. That's why healthcare professionals use BMI alongside other measurements like waist circumference, body fat percentage, and blood markers.
Sources and references
- WHO - Obesity and Overweight
- CDC - About Adult BMI
- National Institutes of Health (NIH)