BMI (WHO) Formula Explained, With Examples
Every bmi (who) result comes from one formula. Once you understand what goes into it, you can sanity-check any figure you are given, whether by an employer, a bank, a teacher or another website.
The formula
BMI = kg ÷ m².
What each input means
- Weight (kg): the value you enter in the calculator.
- Height (cm): the value you enter in the calculator.
Example
For example, with these inputs:
- Weight (kg): 68
- Height (cm): 170
the calculator returns:
- BMI: 23.53
- WHO category: Normal weight
How the result changes
The table keeps the other inputs at their example values and changes weight (kg).
| Weight (kg) | BMI | WHO category |
|---|---|---|
| 68 | 23.53 | Normal weight |
| 34 | 11.76 | Underweight |
| 51 | 17.65 | Underweight |
| 85 | 29.41 | Overweight |
| 102 | 35.29 | Obese |
Why it matters
Health numbers are most useful when you track them consistently. A quick calculation turns everyday measurements into something you can act on, whether that is planning meals, training for a run or preparing for a clinic visit.
Programmes such as the National Steps Challenge and the Healthy 365 app have made tracking activity common. Turning those numbers into distance, pace or calories helps set realistic goals for events like IPPT or a 10 km run.
Singapore's tropical climate means you lose more fluid through sweat, even when you are not exercising. Thirst, urine colour and how you feel are good guides, and needs rise during outdoor activity or heat waves.
Energy needs depend on age, sex, size and activity. Formulas such as Mifflin-St Jeor estimate resting needs, and an activity multiplier turns that into daily needs. Real requirements vary by a few hundred calories, so adjust based on how your weight changes over several weeks.
Related calculations
- Running Pace Calculator: Calculates pace for runs like the Standard Chartered Marathon or IPPT 2.4 km.
- Calories Burned Calculator: Estimates calories burned with MET values.
- BMI Calculator (Asian Cut-offs): Singapore's Health Promotion Board uses lower BMI cut-offs for Asians because health risks rise at lower BMIs.
- BMR Calculator: Estimates calories your body burns at rest.
Use the BMI Calculator (WHO) to plug in your own numbers.
Run your own numbers: BMI Calculator (WHO)