- Healthy weight for your height
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- BMI Prime
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- Ponderal index
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BMI is a screening measure for adults aged 20+, not a diagnosis. It does not distinguish muscle from fat — talk to a healthcare professional about your individual health.
Body Mass Index (BMI) is a quick screening measure that relates weight to height. Enter your measurements in metric or imperial units to see your BMI, category and the healthy weight range for your height.
How to use the BMI Calculator
- 1 Choose metric (kg, cm) or imperial (lb, ft/in) units.
- 2 Enter your weight and height.
- 3 Read your BMI, category and healthy weight range; the gauge shows where you sit.
Formula
BMI = weight (kg) ÷ height (m)² BMI = 703 × weight (lb) ÷ height (in)²
Worked examples
Input: 70 kg, 175 cm
Result: BMI 22.9
Healthy weight (18.5–24.9)
Input: 200 lb, 5 ft 10 in
Result: BMI 28.7
Overweight (25–29.9)
BMI categories for adults (WHO)
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Healthy weight |
| 25.0 – 29.9 | Overweight |
| 30.0 – 34.9 | Obesity class I |
| 35.0 – 39.9 | Obesity class II |
| 40.0 and above | Obesity class III |
Limitations of BMI
BMI does not distinguish muscle from fat or show where fat is stored. Athletes may be classed as overweight despite low body fat, and older adults may have a "healthy" BMI with low muscle mass. Some health bodies recommend lower thresholds for people of South Asian, Chinese and other Asian heritage. Waist circumference and other measures give a fuller picture.
BMI Prime
BMI Prime is your BMI divided by 25 (the upper limit of the healthy range). A value below 1.0 means you are within or below the healthy range.
This calculator provides general estimates for healthy adults and is not medical advice. Consult a doctor or registered dietitian before making significant changes to your diet or exercise.
Frequently asked questions
What is a healthy BMI?
For most adults, a BMI from 18.5 to 24.9 is considered a healthy weight range.
Is BMI accurate for athletes?
Not very — muscular people can have a high BMI without excess fat. Body-fat measurements are more informative for them.
Can children use this BMI calculator?
No. Children and teens need age- and sex-specific BMI percentiles rather than adult categories.
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