Your measurements
For adults 18+. Values convert automatically when you switch unit systems.
Your result
BMI is a population screening measure, not a diagnosis. It says nothing about body composition - talk to a healthcare professional about what is right for you.
Not just a number: you get the WHO category, the healthy weight range for your exact height, and plain-language notes on when BMI misleads.
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BMI categories (WHO classification for adults)
| 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 |
The formula
Metric: BMI = weight (kg) ÷ height (m)². Example: 70 kg at 1.75 m → 70 ÷ 3.0625 = 22.9.
Imperial: BMI = 703 × weight (lb) ÷ height (in)². Example: 154 lb at 5′7″ (67 in) → 703 × 154 ÷ 4,489 = 24.1.
Healthy weight range by height
The weight span that keeps BMI between 18.5 and 24.9 at each height:
| Height | Healthy range (kg) | Healthy range (lb) |
|---|---|---|
| 150 cm · 4′11″ | 41.6 - 56.0 kg | 92 - 123 lb |
| 160 cm · 5′3″ | 47.4 - 63.7 kg | 104 - 140 lb |
| 170 cm · 5′7″ | 53.5 - 72.0 kg | 118 - 159 lb |
| 180 cm · 5′11″ | 59.9 - 80.7 kg | 132 - 178 lb |
| 190 cm · 6′3″ | 66.8 - 89.9 kg | 147 - 198 lb |
| 200 cm · 6′7″ | 74.0 - 99.6 kg | 163 - 220 lb |
What BMI does - and doesn't - measure
BMI was designed as a quick screening statistic for populations, and at that job it is genuinely useful: it needs only a scale and a tape measure, and across large groups it tracks health risk reasonably well. Applied to one individual, it has known blind spots:
- It can't see muscle. Muscle is denser than fat, so strength athletes and very active people often read "overweight" while lean.
- It can't see where fat is stored. Abdominal (visceral) fat drives most metabolic risk; fat on hips and thighs matters far less. Two people with identical BMI can carry very different risk.
- It shifts meaning with age. Older adults lose muscle, so the same BMI represents more fat than it does in a 25-year-old.
- Cutoffs aren't universal. Risk rises at lower BMI in many Asian populations (see FAQ) - several countries use lower national thresholds.
- It doesn't apply to children, pregnant women, or people under 18 - children need age-and-sex percentile charts.
A practical companion check: keep your waist circumference under half your height. Together with blood pressure, blood sugar, and cholesterol, that tells you far more than BMI alone. And for any real decision, the right move is the boring one: talk to a doctor.
Frequently asked questions
What is a healthy BMI?
For most adults, the World Health Organization defines the healthy range as a BMI of 18.5 to 24.9. Below 18.5 is classed as underweight, 25 to 29.9 as overweight, and 30 or above as obesity. These are population-level screening bands, not personal diagnoses - where your individual healthy weight sits depends on factors BMI cannot see.
How do I calculate BMI manually?
Metric: divide your weight in kilograms by your height in meters squared - BMI = kg ÷ m². Example: 70 kg at 1.75 m is 70 ÷ 3.0625 = 22.9. Imperial: multiply your weight in pounds by 703, then divide by your height in inches squared - BMI = 703 × lb ÷ in².
Is BMI accurate for athletes and muscular people?
No - this is BMI's best-known blind spot. It measures weight, not what the weight is made of, and muscle is denser than fat. Strength athletes routinely land in the "overweight" band while carrying very little fat. If you train seriously, waist circumference and body-fat measurements say far more than BMI does.
Does BMI work the same for men, women, and older adults?
The formula and categories are identical for adult men and women, even though body composition differs by sex. In older adults, muscle loss can make BMI flatter than reality - a "healthy" BMI can hide low muscle mass, and some research suggests slightly higher BMI is not harmful in older age. Treat it as one signal among several.
Are BMI categories different for Asian populations?
Yes. Health risks associated with weight appear at lower BMI values in many Asian populations, so WHO expert consultation suggests additional action points: 23 and above as increased risk and 27.5 and above as high risk. Several countries, including Japan, Singapore, and India, use lower national cutoffs than the standard 25/30.
Can I use this BMI calculator for children?
No. For anyone under 18, BMI must be interpreted against age-and-sex growth charts as a percentile, not fixed adult cutoffs - a value that is healthy at 16 can mean something different at 8. Use a dedicated pediatric BMI-percentile tool or ask a pediatrician.
What does BMI miss, and what should I check instead?
BMI cannot see body composition or where fat is stored, and abdominal fat carries most of the metabolic risk. A useful complement is the waist-to-height ratio: keeping waist circumference under half your height is a widely used rule of thumb. Blood pressure, blood sugar, and cholesterol complete the picture better than any single number.
Is my height and weight data uploaded anywhere?
No. Your measurements are processed by JavaScript in your browser and never transmitted, logged, or stored - this page makes no network requests after loading and works offline. Health data is exactly the kind of thing that should never touch someone else's server.