BMI Calculator
WHO BMI classification · By Stuart Mathieson · Updated October 2026
Feet
Inches
Results
Your BMI
Healthy Range
Healthy Weight
Note: BMI is a screening tool, not a diagnostic measure. Consult a healthcare provider for personalized advice.
How the BMI calculator works
Body mass index compares your weight with your height. It is your weight in kilograms divided by your height in meters squared:
In US units the equivalent is BMI = 703 × weight (lb) ÷ height (in)2. This calculator converts imperial inputs to metric first, which gives the same answer.
Worked examples
- 70 kg and 175 cm: 1.75 × 1.75 = 3.0625, and 70 ÷ 3.0625 = 22.9, in the healthy weight range.
- 154 lb and 5 ft 9 in (69 in): 703 × 154 ÷ (69 × 69) = 22.7.
The healthy weight range shown with your result is BMI 18.5 to 24.9 turned back into a weight at your height: 18.5 × height² up to 24.9 × height². For 175 cm, that is 56.7 to 76.3 kg (125 to 168 lb).
BMI categories for adults
These are the cut-offs used by the World Health Organization and the CDC for adults. This calculator groups everything from 30 upward as obese.
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 to 24.9 | Healthy weight |
| 25.0 to 29.9 | Overweight |
| 30.0 to 34.9 | Obesity, class 1 |
| 35.0 to 39.9 | Obesity, class 2 |
| 40.0 and above | Obesity, class 3 (severe obesity) |
Healthy weight range by height
| Height | Healthy weight (kg) | Healthy weight (lb) |
|---|---|---|
| 150 cm (4 ft 11 in) | 41.6 - 56.0 | 92 - 124 |
| 155 cm (5 ft 1 in) | 44.4 - 59.8 | 98 - 132 |
| 160 cm (5 ft 3 in) | 47.4 - 63.7 | 104 - 141 |
| 165 cm (5 ft 5 in) | 50.4 - 67.8 | 111 - 149 |
| 170 cm (5 ft 7 in) | 53.5 - 72.0 | 118 - 159 |
| 175 cm (5 ft 9 in) | 56.7 - 76.3 | 125 - 168 |
| 180 cm (5 ft 11 in) | 59.9 - 80.7 | 132 - 178 |
| 185 cm (6 ft 1 in) | 63.3 - 85.2 | 140 - 188 |
| 190 cm (6 ft 3 in) | 66.8 - 89.9 | 147 - 198 |
What BMI doesn't tell you
- Muscle vs fat. BMI uses total weight, so it can't tell muscle from fat. Muscular people can score as overweight without excess body fat, and some people in the healthy range carry more body fat than their BMI suggests.
- Where fat is stored. Fat around the waist carries more health risk than fat elsewhere. The WHO notes that measurements such as waist circumference can help alongside BMI.
- Ethnicity. A WHO expert consultation found that in many Asian populations, health risks rise at lower BMIs than in European populations, and suggested additional public-health action points at 23 and 27.5.
- Children and teenagers. These adult categories don't apply. A young person's BMI is compared with growth charts for their age and sex instead.
- Pregnancy, older age and some medical conditions also change how BMI should be read.
BMI is a screening tool, not a diagnosis. If your result concerns you, a doctor can look at it alongside other measures such as waist size, blood pressure and blood tests.
Frequently asked questions
Is BMI accurate for everyone?
Not always. BMI doesn't distinguish muscle from fat, so it can overestimate body fat in muscular or athletic people and underestimate it in others. It's a useful general screening tool, not a full health assessment.
What are the BMI categories?
Under 18.5 is underweight, 18.5–24.9 is healthy weight, 25–29.9 is overweight, and 30+ is obese.
Does BMI measure body fat directly?
No - it's a ratio of weight to height only. For a more complete picture, it's often considered alongside measurements like waist circumference or body fat percentage.
Why does my BMI say overweight when I am muscular?
BMI only uses your total weight, and muscle is denser than fat. Athletes and people who do a lot of strength training often have a BMI above 25 without carrying excess body fat.
Sources
- Adult BMI Categories - Centers for Disease Control and Prevention
- About Body Mass Index (BMI) - Centers for Disease Control and Prevention
- Obesity and overweight (fact sheet) - World Health Organization
- Appropriate body-mass index for Asian populations and its implications for policy and intervention strategies - WHO Expert Consultation, The Lancet, 2004