BMI, Ideal Weight & BMR
Body mass index from height and weight.
BMI
0
Enter your height and weight.
What is BMI?
Body Mass Index (BMI) is a simple indicator of body weight status calculated from height and weight. It is widely used by the WHO and health screenings because it requires no special equipment, but it cannot distinguish muscle mass from body fat, so it should be treated as a reference indicator rather than a definitive diagnosis.
How it is calculated
BMI = weight (kg) ÷ (height (m))²
For example, a person 170cm (1.7m) tall weighing 65kg has a BMI of 65 ÷ (1.7 × 1.7) ≈ 22.5, which falls within the normal range (18.5–22.9). Ideal weight is commonly estimated as 22 × (height in m)², which is about 63.6kg in this example.
Ideal weight & obesity level
Ideal weight estimates a healthy body weight based on height, commonly calculated as 22 × (height in m)² (BMI 22). Obesity level (%) = current weight ÷ ideal weight × 100. Under 90% is underweight, 90–110% is normal, 110–120% is overweight, and over 120% is obese.
BMR & TDEE
This calculator uses the Mifflin-St Jeor equation for BMR.
Male BMR = 10×weight(kg) + 6.25×height(cm) − 5×age + 5
Female BMR = 10×weight(kg) + 6.25×height(cm) − 5×age − 161
TDEE = BMR × activity factor. Eat below TDEE to lose weight, above TDEE to gain weight.
Why Korean and international thresholds differ
A BMI of 24 can read as normal or overweight depending on the table used: the thresholds applied in Korea are lower than the WHO international standard.
The Asia-Pacific standard
The WHO international standard treats 25 and above as overweight and 30 and above as obese. Korean practice uses 23 and 25 respectively, which is what the table above follows.
The difference reflects evidence that body fat and metabolic risk differ by ethnicity at the same BMI: East Asian populations show elevated diabetes and hypertension risk at lower values, prompting a separate Asia-Pacific standard.
Calculators on overseas sites can therefore disagree with a domestic health check, which applies the Korean thresholds.
What BMI misses
BMI is only weight over height squared and cannot distinguish body composition: muscular people score high with little fat, while low muscle and high fat can pair a normal BMI with elevated metabolic risk.
It also ignores where fat sits. Abdominal fat carries greater cardiovascular risk at the same weight, and BMI does not separate the two.
Adult thresholds do not transfer to children, pregnancy or older adults. Children use age- and sex-specific percentiles, and in older adults a somewhat higher BMI has been associated with lower mortality.
Measures worth checking alongside
Waist circumference measures abdominal fat directly and complements BMI. Korean thresholds are 90 cm for men and 85 cm for women, and a tape measure is all it takes.
The waist-to-hip ratio is also used, indicating whether fat is concentrated in the upper or lower body.
Body composition analysis measures fat and muscle directly, though readings vary with the device and conditions — trends under consistent conditions are more useful than single values. No single measure settles the question; blood pressure, glucose and lipids belong in the picture.
Legal basis
- Korean diagnostic criteria — Korean Society for the Study of Obesity guidelines
- Asia-Pacific standard — WHO/IASO/IOTF, The Asia-Pacific Perspective (2000)
- International standard — WHO, Obesity: Preventing and Managing the Global Epidemic
- Waist circumference thresholds — Korean Society for the Study of Obesity