Method · Body measurements
BMI calculator
What your body mass index means, the World Health Organization categories Bud uses, and the healthy weight range for your height.
Work out your BMI
WHO categoriesYour BMI
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BMI is a screening measure, not a diagnosis. It doesn't apply in pregnancy or to children, and a doctor or dietitian can tell you what yours means for you.
How BMI is worked out
Body mass index is your weight divided by the square of your height. It's quick to measure and the same everywhere, so it is how the World Health Organization tracks weight across populations1.
What the number means
These are the WHO's categories for adults1, and the ones the BMI card in Bud uses:
| BMI | WHO category |
|---|---|
| Under 18.5 | Underweight |
| 18.5 – 24.9 | Healthy weight |
| 25 – 29.9 | Overweight |
| 30 and over | Obese |
The healthy weight for your height
A category on its own isn't much to act on. The weight range that puts you in the healthy band is, so Bud shows it beside your BMI. It is the healthy band worked backwards:
Bud also uses the top of that range to set your protein target if you're above it, because muscle rather than body fat is what sets how much protein you need. The calorie & macro calculator explains how.
A note for Indians and other South Asians
At the same BMI, South Asians tend to carry more body fat, and more of it around the waist, than people of European origin - and with it a higher risk of type 2 diabetes and heart disease. A 2004 WHO expert consultation found that for many Asian populations this risk is already substantial below a BMI of 25. It kept the international categories, but suggested additional public-health "action points" at 23 and 27.52. India's 2009 consensus guidelines go further and use a BMI of 23 for overweight and 25 for obesity3.
Bud shows WHO's categories, so a BMI of 24 reads as healthy, as it does in the international standard. If yours is between 23 and 25, it's worth knowing that India's guidelines would call it overweight - and worth asking a doctor what it means for you, especially if diabetes or heart disease runs in your family.
What BMI can't tell you
- Muscle from fat. A muscular person can read as overweight with very little body fat.
- Where the fat is. Fat around the waist carries more risk than fat elsewhere, and BMI can't see it. A tape measure around your waist adds what BMI misses.
- Everyone. It doesn't apply in pregnancy, and children and teenagers are judged against growth charts rather than these categories.
Common questions
How is BMI calculated?
Divide your weight in kilograms by your height in metres squared. For example, 70 kg at 1.65 m is 70 ÷ (1.65 × 1.65) = 25.7.
What is a healthy BMI?
The World Health Organization classes a BMI of 18.5 to 24.9 as healthy, under 18.5 as underweight, 25 to 29.9 as overweight and 30 or more as obese1.
Is the healthy BMI different for Indians?
Some guidelines say yes. A 2004 WHO expert consultation suggested additional action points at 23 and 27.5 for many Asian populations while keeping the international categories2, and India's 2009 consensus guidelines use 23 for overweight and 25 for obesity3. Bud shows the WHO categories, so its numbers match the international standard.
What is the healthy weight for my height?
Multiply your height in metres squared by 18.5 and by 24.9. For someone 1.60 m tall that is about 47 to 64 kg - the calculator above works it out for you.
Is BMI accurate?
It's a quick screening measure, not a diagnosis. It can't tell muscle from fat or show where fat is stored, so a muscular person can read as overweight. Waist size adds useful information, and BMI doesn't apply in pregnancy or to children.
References
- World Health Organization. Body mass index (BMI). Global Health Observatory. who.int/data/ghoThe international BMI categories for adults.
- WHO Expert Consultation. Appropriate body-mass index for Asian populations and its implications for policy and intervention strategies. Lancet. 2004;363(9403):157–163. doi.org/10.1016/S0140-6736(03)15268-3Higher risk below a BMI of 25 in many Asian populations; additional public-health action points at 23 and 27.5.
- Misra A, Chowbey P, Makkar BM, et al. Consensus statement for diagnosis of obesity, abdominal obesity and the metabolic syndrome for Asian Indians and recommendations for physical activity, medical and surgical management. J Assoc Physicians India. 2009;57:163–170. pubmed.ncbi.nlm.nih.gov/19582986Overweight from a BMI of 23 and obesity from 25 for Asian Indians.