How to use the BMI Calculator
- Choose your units: kg + cm, kg + feet or lb + feet.
- Enter your height and weight.
- Press “Calculate” to see your BMI and category.
BMI formula and categories
BMI = weight (kg) ÷ height (m)². The World Health Organization uses these adult categories:
- Below 18.5: underweight
- 18.5 – 24.9: healthy weight
- 25.0 – 29.9: overweight
- 30.0 and above: obesity
BMI in kg and feet
Many people know their weight in kilograms but their height in feet and inches. Choose “kg + feet” to enter exactly that, or use “kg + cm” or “lb + feet” – the calculator converts everything for you. For example, 5 ft 6 in is 167.6 cm; at 70 kg that gives a BMI of 24.9.
BMI for men, women and different ages
For adults aged 18 and over, the same BMI categories apply to men and women and do not change with age. Women naturally carry more body fat than men at the same BMI, and older adults may carry more fat for the same BMI, which is why BMI is a screening number, not a diagnosis.
For people of South Asian, Chinese and other Asian backgrounds, the WHO suggests extra cut-off points: 23 as increased risk and 27.5 as high risk.
What BMI does not tell you
BMI does not distinguish muscle from fat, so muscular people can have a high BMI while being healthy. It also does not show where fat is stored. Some health bodies use lower thresholds for people of Asian descent (for example 23 for overweight). BMI categories do not apply to children and teens, who need age-specific charts.
Frequently asked questions
How do I calculate BMI with weight in kg and height in feet?
Select “kg + feet”, enter your weight in kilograms and your height in feet and inches, then press “Calculate”. You can also use kg + cm or lb + feet.
Is BMI different for men and women?
No. Adult BMI uses the same formula and categories for men and women, although body fat at the same BMI differs.
What is a healthy BMI?
For most adults, a BMI between 18.5 and 24.9 is considered a healthy range.
Is BMI accurate for athletes?
Not always. Muscle weighs more than fat, so athletes can have a high BMI without excess body fat.
Can children use this calculator?
No. Children and teenagers need BMI-for-age percentile charts.