How BMI is calculated
Body Mass Index compares your weight to your height. It's the same formula in any unit system. The US version just includes a conversion factor.
Example: someone 5 ft 9 in (69 in) tall weighing 165 lb has a BMI of 703 × 165 ÷ 69² = 24.4, in the healthy range.
Adult BMI categories
These are the standard categories used by the CDC and the World Health Organization for adults 20 and older:
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Healthy weight |
| 25.0 – 29.9 | Overweight |
| 30.0 – 34.9 | Obesity (Class 1) |
| 35.0 – 39.9 | Obesity (Class 2) |
| 40.0 and above | Obesity (Class 3) |
BMI is quick and useful for populations, but it's an imperfect measure for individuals. Athletes with a lot of muscle can score as "overweight", and it says nothing about where fat is carried. For children and teens, BMI is interpreted with age- and sex-specific percentiles instead. Talk to a healthcare provider about what your number means for you.
Healthy weight range by height
Whole-pound weights that give an adult BMI from 18.5 up to (but not including) 25. Weight = BMI × height (in)² ÷ 703.
| Height | Healthy weight range | BMI 25 (overweight) starts at | BMI 30 (obesity) starts at |
|---|---|---|---|
| 4 ft 10 in | 89 to 119 lb | 120 lb | 144 lb |
| 5 ft 0 in | 95 to 128 lb | 129 lb | 154 lb |
| 5 ft 2 in | 102 to 136 lb | 137 lb | 165 lb |
| 5 ft 4 in | 108 to 145 lb | 146 lb | 175 lb |
| 5 ft 6 in | 115 to 154 lb | 155 lb | 186 lb |
| 5 ft 8 in | 122 to 164 lb | 165 lb | 198 lb |
| 5 ft 10 in | 129 to 174 lb | 175 lb | 210 lb |
| 6 ft 0 in | 137 to 184 lb | 185 lb | 222 lb |
| 6 ft 2 in | 145 to 194 lb | 195 lb | 234 lb |
| 6 ft 4 in | 152 to 205 lb | 206 lb | 247 lb |
These ranges apply to adults 20 and older. Children and teens are measured against age and sex percentiles instead.
Next steps
BMI can't tell muscle from fat, so for a fuller picture estimate your body fat percentage with a tape measure, and use the calorie calculator to plan how much to eat.
Frequently asked questions
Is BMI accurate?
BMI is a useful screening tool but not a direct measure of body fat or health. Waist circumference, blood pressure, blood tests and a doctor's assessment give a fuller picture.
Can I use this for children?
No. Children and teens (ages 2–19) use BMI-for-age percentiles from growth charts, because healthy body composition changes as they grow.
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