BMI Calculator
Calculate your Body Mass Index with support for all units — metric and imperial — and 4 international standards including Asian-specific thresholds.
Enter Your Details
Your Results
Fill in your details on the left
Results appear here instantly
What is BMI?
Body Mass Index (BMI) is a numerical value calculated from a person's weight and height. It was devised by Belgian mathematician Adolphe Quetelet in the 1830s and is used as a screening tool to categorize a person's weight relative to their height.
WHO Classification (International)
| BMI | Category |
|---|---|
| < 16.0 | Severely Underweight |
| 16.0–17.0 | Moderately Underweight |
| 17.0–18.5 | Mildly Underweight |
| 18.5–25.0 | Normal Weight |
| 25.0–30.0 | Overweight (Pre-obese) |
| 30.0–35.0 | Obese Class I |
| 35.0–40.0 | Obese Class II |
| ≥ 40.0 | Obese Class III |
Asian Standards (Lower Thresholds)
| BMI | Category (HK) |
|---|---|
| < 18.5 | Underweight |
| 18.5–23.0 | Normal |
| 23.0–25.0 | Overweight I |
| 25.0–30.0 | Overweight II |
| ≥ 30.0 | Obese |
BMI and Gender Differences
While the BMI formula is the same for men and women, body composition differs significantly between sexes at the same BMI value. Women naturally carry more body fat than men at an equivalent BMI.
Male Body Fat Ranges
| Essential fat | 2–5% |
| Athletic | 6–13% |
| Fit | 14–17% |
| Acceptable | 18–24% |
| Obese | 25%+ |
Female Body Fat Ranges
| Essential fat | 10–13% |
| Athletic | 14–20% |
| Fit | 21–24% |
| Acceptable | 25–31% |
| Obese | 32%+ |
This calculator estimates body fat percentage using the Deurenberg formula: %BF = (1.20 × BMI) + (0.23 × Age) − (10.8 × sex) − 5.4
What is BMI Prime?
BMI Prime is the ratio of your BMI to the upper limit of the normal range (25 kg/m²). A BMI Prime of 1.0 means you are at the upper boundary of normal weight.
Frequently Asked Questions
Related Tools
Waist to Hip Ratio Calculator
Calculate your waist-to-hip ratio (WHR) and check cardiovascular risk using WHO standards. Supports cm and inches.
Water Intake Calculator
Calculate daily water intake based on weight, activity level, exercise, and climate. Shows glasses and bottles needed.
Target Heart Rate Zone Calculator
Calculate your target heart rate training zones from age and resting heart rate. Uses max HR (220-age) and the Karvonen formula for precise cardio zones.
Steps to Distance (Miles/KM) Calculator
Convert your step count into walking or running distance in miles and km, or find how many steps a target distance takes. Based on height and pace.
Baby Growth Percentile Calculator
Calculate your baby or toddler's weight, length, and head circumference percentile for age using CDC/WHO growth chart standards. Free, instant, for ages 0–36 months.
Intermittent Fasting Window & Timer Calculator
Free intermittent fasting calculator and timer. Pick 16:8, 18:6, 20:4, OMAD, 14:10, or a custom schedule to see when your fast ends and your eating window opens.
Barbell Plate Loading Calculator
Enter your target weight and bar type to see exactly which plates to load on each side of the barbell. Supports kg and lb, Olympic and training bars, and custom plate sets.
Medical Disclaimer
This BMI calculator is for informational and educational purposes only. BMI is a screening tool and should not be used as a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional for health concerns.