Body Mass Index (BMI) is the most widely used screening tool for assessing whether an adult's weight is in a healthy range for their height. It's used by GPs, nurses, and health organisations worldwide as a starting point for health conversations. This guide explains how to read BMI charts, what the numbers mean, and the limitations you should know about.
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Enter your height and weight for an instant result.BMI Categories (WHO Standard)
The World Health Organisation (WHO) defines BMI categories for adults as follows. These are the same ranges used by the NHS in the UK and the CDC in the US:
| Category | BMI Range | Health Implication |
|---|---|---|
| Underweight | Below 18.5 | May indicate nutritional deficiency |
| Healthy Weight | 18.5 – 24.9 | Associated with lowest health risk |
| Overweight | 25.0 – 29.9 | Increased risk of some conditions |
| Obese (Class I) | 30.0 – 34.9 | High risk — medical review advised |
| Obese (Class II) | 35.0 – 39.9 | Very high risk |
| Severely Obese (Class III) | 40.0 and above | Extremely high risk |
BMI Chart by Height and Weight (Metric)
This chart shows the approximate BMI for common height and weight combinations. Find your height in the left column and your weight across the top to estimate your BMI category.
| Height | 50kg | 60kg | 70kg | 80kg | 90kg | 100kg | 110kg |
|---|---|---|---|---|---|---|---|
| 1.55m | 20.8 | 25.0 | 29.1 | 33.3 | 37.5 | 41.6 | 45.8 |
| 1.60m | 19.5 | 23.4 | 27.3 | 31.3 | 35.2 | 39.1 | 43.0 |
| 1.65m | 18.4 | 22.0 | 25.7 | 29.4 | 33.1 | 36.7 | 40.4 |
| 1.70m | 17.3 | 20.8 | 24.2 | 27.7 | 31.1 | 34.6 | 38.1 |
| 1.75m | 16.3 | 19.6 | 22.9 | 26.1 | 29.4 | 32.7 | 35.9 |
| 1.80m | 15.4 | 18.5 | 21.6 | 24.7 | 27.8 | 30.9 | 34.0 |
| 1.85m | 14.6 | 17.5 | 20.5 | 23.4 | 26.3 | 29.2 | 32.1 |
| 1.90m | 13.9 | 16.6 | 19.4 | 22.2 | 24.9 | 27.7 | 30.5 |
🟦 Underweight 🟩 Healthy 🟨 Overweight 🟧 Obese Class I 🟥 Obese Class II+
The BMI Formula
Example: A person who is 1.75m tall and weighs 75kg has a BMI of: 75 ÷ (1.75 × 1.75) = 75 ÷ 3.0625 = 24.5 — which falls in the Healthy range.
Use our free BMI calculator to get your result instantly without doing the maths yourself.
BMI for Different Ethnic Groups
The standard WHO BMI thresholds were developed primarily using Western populations. Research shows that people of South Asian, East Asian, and some other ethnic backgrounds may have a higher risk of weight-related health conditions at lower BMI values. The NHS uses adjusted thresholds for some groups:
- For people of South Asian, Chinese, or Black African/Caribbean background, the NHS considers a BMI of 23 or above as overweight (rather than 25).
- Obesity is defined at BMI 27.5 for these groups (rather than 30).
The Limitations of BMI
BMI has real and well-documented limitations:
- It doesn't distinguish muscle from fat. A heavily muscled athlete may have a BMI in the "overweight" or "obese" range despite having very low body fat.
- It doesn't show where fat is stored. Visceral fat (around the abdomen) is more health-damaging than subcutaneous fat, but BMI can't distinguish between them.
- It's not calibrated for older adults. Older adults typically lose muscle mass, so a "healthy" BMI may mask low muscle mass in someone over 65.
- It doesn't account for bone density. People with denser bones will weigh more at the same body fat percentage.
For a fuller picture, doctors often combine BMI with waist circumference measurements and other health indicators like blood pressure and blood glucose levels.
Frequently Asked Questions
What is a healthy BMI for adults?
For most adults, a BMI between 18.5 and 24.9 is considered a healthy weight range. Below 18.5 is underweight; 25–29.9 is overweight; 30 and above is classified as obese.
Is BMI accurate for women and men?
The same BMI thresholds apply to both men and women, though women typically have a higher percentage of body fat at the same BMI as men. Some researchers suggest slightly different healthy ranges by sex, but the WHO and NHS use the same ranges for both.
Is BMI an accurate measure of health?
BMI is a useful first-step screening tool but has significant limitations — it doesn't account for muscle mass, fat distribution, age, or ethnicity. Always discuss your weight and health with a qualified healthcare professional.
How do I calculate my BMI?
BMI = weight in kg ÷ (height in metres)². Or just use our free BMI calculator for an instant result.