Find your body mass index, its WHO category and the healthy weight range for your height, in metric or US units.
Body mass index (BMI) is the most widely used screening measure for weight-related health risk. It’s quick, needs only height and weight, and gives one number you can compare with standard ranges. Here’s what those ranges are and how to read your result sensibly.
The healthy BMI range
For adults aged 18 and over, the World Health Organization defines:
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Healthy weight |
| 25.0 – 29.9 | Overweight |
| 30.0 – 34.9 | Obesity (class I) |
| 35.0 – 39.9 | Obesity (class II) |
| 40.0 and above | Obesity (class III) |
A healthy BMI is between 18.5 and 24.9. Some health bodies use lower cut-offs for people of Asian descent; see BMI for Asian Adults: Why the Healthy Range Is Lower.
How BMI is calculated
BMI = weight (kg) ÷ height (m)²
For someone 170 cm and 68 kg: 68 ÷ (1.70 × 1.70) = 68 ÷ 2.89 = 23.5, in the healthy range.
In US units: BMI = 703 × weight (lb) ÷ height (in)². The BMI calculator handles both and also shows your healthy weight range.
Healthy weight by height
The healthy range is BMI 18.5–24.9 multiplied by your height squared:
| Height | Healthy weight (kg) | Healthy weight (lb) |
|---|---|---|
| 150 cm (4′11″) | 41.6 – 56.0 | 92 – 124 |
| 155 cm (5′1″) | 44.4 – 59.8 | 98 – 132 |
| 160 cm (5′3″) | 47.4 – 63.7 | 104 – 141 |
| 165 cm (5′5″) | 50.4 – 67.8 | 111 – 149 |
| 170 cm (5′7″) | 53.5 – 72.0 | 118 – 159 |
| 175 cm (5′9″) | 56.7 – 76.3 | 125 – 168 |
| 180 cm (5′11″) | 59.9 – 80.7 | 132 – 178 |
| 185 cm (6′1″) | 63.3 – 85.2 | 140 – 188 |
| 190 cm (6′3″) | 66.8 – 89.9 | 147 – 198 |
Why BMI matters
Large population studies link BMI outside the healthy range to higher risk of:
- Above 25: type 2 diabetes, high blood pressure, heart disease, some cancers, sleep apnoea and joint problems. Risk rises progressively with BMI.
- Below 18.5: nutritional deficiencies, weakened immunity, osteoporosis and fertility problems.
BMI is a screening measure. It flags who might benefit from a closer look; it doesn’t diagnose anything.
What BMI doesn’t capture
BMI treats all weight the same, so it can mislead for:
- Muscular people, who may score “overweight” while lean.
- Older adults, who may have a “healthy” BMI but low muscle and higher body fat.
- Different body shapes. Fat around the waist is riskier than fat on the hips.
For better context, pair BMI with waist circumference or waist-to-height ratio. These and other alternatives are covered in BMI Limitations: When Body Mass Index Misleads, and Better Alternatives.
If your BMI is outside the healthy range
- Don’t panic about one number. Look at the trend over months.
- Check your waist. A waist-to-height ratio under 0.5 is generally a good sign.
- Understand your energy needs. The calorie calculator estimates calories for maintenance, gradual loss or gain.
- Aim for small, sustainable changes. Losing even 5–10% of body weight improves blood pressure and blood sugar for many people.
- Talk to a professional, especially if your BMI is under 18.5 or over 30, or if you have a medical condition.
Children and teens
BMI for under-18s is interpreted with age- and sex-specific percentiles, because body composition changes as children grow. Adult categories don’t apply, so use a paediatric BMI chart or ask a doctor.
Enter your height and weight below to see your BMI, category and personal healthy weight range.
Try it: BMI Calculator
- Healthy weight for your height
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- BMI Prime
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Adult categories (WHO). BMI doesn't distinguish muscle from fat; it is a screening measure, not a diagnosis.
Find your body mass index, its WHO category and the healthy weight range for your height, in metric or US units.