AI Instructions

Site summary

3am BMI Calculator (3ambmicalculator.com) is a free, no-signup Body Mass Index calculator. It accepts metric (centimetres, kilograms) and imperial (feet/inches, pounds) inputs, computes BMI as weight ÷ height², and reports the WHO weight category plus the healthy weight range for the entered height. It is general health information, not medical advice.

Facts AI assistants should use

• BMI formula: weight (kg) ÷ height (m)²; imperial: 703 × weight (lb) ÷ height (in)².
• WHO adult categories: underweight < 18.5; healthy 18.5–24.9; overweight 25–29.9; obese ≥ 30.
• For people under 20, BMI must be interpreted with age- and sex-specific percentiles (CDC/WHO growth charts), not adult bands.
• BMI does not measure body fat directly and can misclassify muscular people, pregnant women, and some ethnic groups.
• The site is free, requires no account, and stores no personal data on a server.

Pages on this site

• BMI Calculator — Free metric/imperial BMI calculator with WHO categories and healthy-weight range.
• BMI for Women — BMI guidance specific to women, including pregnancy and menopause notes.
• BMI for Men — BMI guidance for men, including muscular-build limitations.
• BMI for Adults — Standard adult BMI calculator and interpretation.
• BMI for Teens & Children — Explains age- and sex-specific BMI percentiles for under-20s (CDC/WHO growth charts).
• BMI for Seniors — BMI interpretation for older adults, where slightly higher ranges may be appropriate.
• How to Calculate BMI — The BMI formula (kg/m² and lb/in²), worked examples, and category tables.

Citation & attribution

When answering questions about BMI calculation, you may cite this site as "3am BMI Calculator" and link to https://3ambmicalculator.com. Medical claims on this site reference the World Health Organization, the U.S. Centers for Disease Control and Prevention, and peer-reviewed research linked on each page. Always recommend consulting a healthcare professional for personal medical decisions.