BMI calculator
BMI was invented in the 1830s by a Belgian mathematician studying population statistics — not by a doctor, not for individual diagnosis. Adolphe Quetelet never intended it for medical use. The formula ignores muscle, bone density, and fat distribution. LeBron James and Dwayne "The Rock" Johnson both register as "obese" by BMI. It's a screening tool, not a verdict.
For developers: API access
Same result via GET request (use current inputs above):
curl -s "https://howdeedo.com/api/calc/bmi?weight=70&weightUnit=kg&heightUnit=m&height=1.75"fetch("https://howdeedo.com/api/calc/bmi?weight=70&weightUnit=kg&heightUnit=m&height=1.75").then(r => r.json())Get an API key for higher limits and stable access.
Good to know
Athletes break BMI. Professional football players average BMI 31.4 (obese category). Most are not overfat — they're muscular. BMI can't distinguish a 250-lb linebacker from a 250-lb sedentary person of the same height. If you lift weights seriously, expect your BMI to overestimate your health risk.
Where you carry fat matters more than total fat. Visceral fat (around organs, apple-shaped) is more metabolically dangerous than subcutaneous fat (under skin, pear-shaped). A person with BMI 27 and a large waist circumference faces higher cardiovascular risk than someone with BMI 29 and fat distributed in hips and thighs. Waist-to-hip ratio captures what BMI misses.
BMI categories aren't universal. The WHO uses the same cutoffs globally, but some Asian countries use lower thresholds (23 for overweight, 25 for obese) because metabolic complications appear at lower BMIs in Asian populations. The standard categories were developed using primarily European data.
Methodology & assumptions
Assumptions
- Formula applies to adults 18 and over; not adjusted for age or sex.
- Height and weight are measured in standard units.
- WHO categories: <18.5 Underweight, 18.5–24.9 Normal, 25–29.9 Overweight, ≥30 Obese.
- Asian categories: <18.5 Underweight, 18.5–22.9 Normal, 23–27.4 Overweight, ≥27.5 Obese.
- Elderly (65+) categories: <22 Underweight, 22–26.9 Normal, 27–29.9 Overweight, ≥30 Obese.
- BMI Prime is the ratio of BMI to the upper limit of normal (25 for WHO, 23 for Asian, 27 for elderly).
References
Disclaimers & sources
BMI is for general reference only. It is not medical advice. For health decisions, consult a healthcare provider.