What BMI tells you
Body mass index is weight in kilograms divided by height in metres squared. The World Health Organization classes adults below 18.5 as underweight, 18.5 to 24.9 as normal, 25 to 29.9 as overweight and 30 or above as obese. Some Asian populations, including South Asians, face higher metabolic risk at lower BMI values, so health bodies in the region often use 23 as an overweight threshold. Ask your doctor which cut-off suits you.
Limits of BMI
BMI is a screening number, not a diagnosis. It does not separate muscle from fat, ignores where fat is stored and does not account for age, pregnancy or athletic build. Waist circumference, blood pressure, blood sugar and family history give a fuller picture. Children and teenagers are assessed with age and sex-specific growth charts, not adult categories, so use a paediatrician's chart for them.
How to use it
- Enter your height in centimetres and weight in kilograms (or switch units if offered).
- Read your BMI, the category and your suggested weight range.
- Use the result to start a conversation with a doctor, not to self-diagnose.
Applying for a service that sets fitness standards? Check the armed forces jobs guide and confirm the exact standards in the official advertisement.
Worked example
A person who is 170 cm tall and weighs 70 kg has a BMI of 70 divided by (1.70 x 1.70), which is 70 / 2.89 = 24.2. That sits in the normal range of 18.5 to 24.9. The healthy weight range for 170 cm is about 53.5 to 72 kg. At 80 kg the BMI would be 27.7, in the overweight range.
Beyond BMI
- Waist circumference: a waist above about 90 cm for men or 80 cm for women is often used as a South Asian risk marker.
- Blood pressure and blood sugar: these show metabolic health better than weight alone.
- Activity and diet: 150 minutes of moderate exercise a week is a common recommendation.
- Family history: diabetes and heart disease risk matter in Pakistan, where both are widespread.
When to see a doctor
If your BMI is under 18.5 or above 25, or if you have sudden weight change, ask a doctor or dietitian for advice instead of following social media diets. Pregnant women, children and older adults need specialised assessment. For fitness standards in uniformed services, read our armed forces guide and check the age limit with the age calculator. Convert pounds and feet with the unit converter and build a routine with the study planner or the Pomodoro timer.
Frequently asked questions
How is BMI calculated?
Weight in kg divided by height in metres squared.
What is a normal BMI?
18.5 to 24.9 under WHO adult categories. Some health bodies suggest lower cut-offs for South Asians.
Is BMI accurate for athletes?
Not always. Muscle weighs more than fat, so a muscular person can show a high BMI at low body fat.
Can I use this for children?
No. Children need age and sex-specific percentile charts from a paediatrician.