BMI Calculator
Use this free BMI calculator to find your body mass index in seconds. Enter your height and weight in metric or imperial units and you'll see your BMI, what category it falls in, and the healthy weight range for your height. Works for adults and for children and teens aged 2 to 19.
BMI compares your weight to your height. For adults, a BMI of 18.5 to 24.9 is the healthy range, 25 to 29.9 is overweight, and 30 or more is obesity. BMI is a quick screening number, not a diagnosis: it doesn't measure body fat directly, so muscular people can score high and older adults can score low. Pair it with your waist-to-height ratio for a fuller picture.
Body Mass Index (BMI)
Healthy (18.5 – 24.9)For adults, healthy weight is defined as a BMI of 18.5 to 24.9.
Healthy Weight
56.7 – 76.3 kg
For your height
Status
In healthy range
WHO Adult BMI Categories
| Classification | Standard BMI | Asian Cut-Off |
|---|---|---|
| Underweight | < 18.5 | < 18.5 |
| Healthy Weight | 18.5 – 24.9 | 18.5 – 22.9 |
| Overweight | 25.0 – 29.9 | 23.0 – 27.4 |
| Obesity Class I | 30.0 – 34.9 | 27.5 – 34.9 |
| Obesity Class II | 35.0 – 39.9 | 35.0 – 39.9 |
| Obesity Class III | ≥ 40.0 | ≥ 40.0 |
Asian cut-offs reflect higher cardiovascular and diabetes risks at lower BMI thresholds.
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Instant Live Maths
Calculates in real time as you type
Clinical Equations
WHO, CDC, ACSM & Mifflin-St Jeor
Suggest a Feature or Improvement for BMI Calculator
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How to use BMI Calculator
- 1Choose your sex and age (adult or child/teen aged 2–19).
- 2Enter your height and weight in metric (kg, cm) or imperial (lb, ft/in).
- 3View your BMI score, WHO weight classification or CDC percentile, and healthy weight range.
What your BMI means
Body Mass Index (BMI) evaluates whether your body weight is in a healthy proportion to your height. Standard adult categories established by the World Health Organization (WHO) are: under 18.5 underweight, 18.5–24.9 healthy weight, 25.0–29.9 overweight, and 30.0 or higher obesity.
For children and teens aged 2 to 19, BMI is assessed against official CDC growth charts using exact age and sex percentiles. A percentile between the 5th and 85th percentiles reflects a healthy weight.
Asian population BMI cut-offs
Public health research shows that Asian populations often exhibit a higher percentage of body fat and elevated cardiometabolic risk at lower BMI levels than European populations. The WHO Western Pacific Region guidelines define overweight at BMI 23.0 and obesity at BMI 27.5 or above.
Limitations of BMI
BMI does not directly measure body composition or differentiate between muscle mass, bone density, and adipose fat. Muscular athletes often register as overweight or obese, while older individuals with low muscle mass may show a normal BMI despite higher body fat.
Frequently Asked Questions
What is a healthy BMI?
For most adults a BMI of 18.5 to 24.9 is considered healthy. Some Asian health bodies use a lower range of 18.5 to 22.9 because health risks rise at lower BMIs in these populations.
How do I calculate BMI in kg and feet?
Convert height to metres (1 ft = 0.3048 m, 1 in = 0.0254 m), then divide weight in kg by height in metres squared. The calculator does this for you automatically when you select imperial units.
Is BMI different for men and women?
The adult formula and categories are the same. For children and teens aged 2 to 19, results are evaluated against CDC growth percentiles based on age and sex.
Is BMI accurate for athletes?
Not always. Muscle weighs more than fat for its volume, so muscular people may show as overweight. A body fat calculator or waist-to-height measurement provides a more accurate picture.
Can I use BMI when pregnant?
No. Standard BMI ranges do not apply during pregnancy. Use your pre-pregnancy BMI as a baseline and consult your midwife or obstetrician for healthy gestational weight gain guidance.
Related Calculators
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Body Fat Calculator
Estimate your body fat percentage using the US Navy tape method or Deurenberg BMI equation.
BMR Calculator
Calculate your Basal Metabolic Rate using Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle.
Calorie Calculator
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Estimate your Total Daily Energy Expenditure and discover your true maintenance calories.
Scientific Sources & Evidence
- World Health Organization (WHO) — Body Mass Index Classification
- CDC Growth Charts — BMI-for-age LMS Percentiles
- Mifflin et al. (1990) — Basal Metabolic Rate Predictive Equations
- NICE Guideline NG246 — Identification and Management of Overweight and Obesity
- American College of Sports Medicine (ACSM) — Exercise Testing & Prescription
- European Food Safety Authority (EFSA) — Dietary Reference Values for Water