BMI Calculator
BMI is a screening measure and does not determine medical fitness for sea service.
SeafarerFit provides educational information, health calculators, screening tools and medical-examination preparation resources. It does not provide diagnosis, treatment, medical certification or official determination of fitness for sea service.
Your answers are calculated in your browser and are not sent to SeafarerFit.
What is BMI?
Body Mass Index (BMI) is your weight in kilograms divided by the square of your height in metres. Health organizations use it as a quick, low-cost way to screen adult populations for weight categories that are linked to health risk.
General adult BMI categories
| BMI (kg/m²) | General category (WHO adult classification) |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Healthy (normal) weight range |
| 25.0 – 29.9 | Overweight (pre-obesity) |
| 30.0 – 34.9 | Obesity class I |
| 35.0 – 39.9 | Obesity class II |
| 40.0 and above | Obesity class III |
These categories apply to adults aged 18 and over. Children and teenagers are assessed with age- and sex-specific growth references instead. Some health authorities use lower cut-off points for people of Asian descent, because health risks can rise at a lower BMI.
What BMI cannot tell you
- It does not separate muscle from fat, so very muscular people can have a high BMI.
- It does not show where fat is stored. Waist size adds useful information.
- It does not measure fitness, blood pressure, blood sugar or any other aspect of health.
BMI and seafarer medical examinations
Your height and weight are commonly measured during a seafarer medical examination, but BMI on its own does not decide whether you are medically fit for sea service. That decision is made by an authorized medical examiner using the standards that apply in your jurisdiction, taking your overall health and duties into account.
BMI is a screening measure and does not determine medical fitness for sea service. If you have health concerns, discuss them with an appropriately qualified healthcare professional.
Frequently asked questions
Is the BMI calculator an official maritime medical test?
No. It is an educational screening tool. Official decisions are made only by an authorized medical examiner.
Does BMI decide whether I can join the Merchant Navy?
No. Medical fitness for sea service is assessed as a whole by an authorized medical examiner using the standards that apply in your jurisdiction.
Is my data saved?
No. The calculation happens in your browser and nothing you type is sent to SeafarerFit.
Sources
- World Health Organization — Obesity and overweight — fact sheet (adult BMI definitions) (opens in a new tab)
- WHO Expert Consultation — Appropriate body-mass index for Asian populations (The Lancet, 2004) (opens in a new tab) (January 10, 2004)
Links go to the original publishers. SeafarerFit is not affiliated with or endorsed by these organizations.