About this tool
Body Mass Index (BMI) is a screening ratio, not a diagnosis: it is your weight in kilograms divided by the square of your height in metres, and a single number cannot tell anyone how healthy they are. The calculator on this page applies the adult categories used by the World Health Organization (WHO): below 18.5 is underweight, 18.5 to 24.9 is normal weight, 25.0 to 29.9 is overweight, and 30.0 or above is obesity. It accepts metric entries (kilograms and centimetres) or imperial entries (pounds, feet and inches) and shows the result to one decimal place with its category. For people in Cambodia, one more distinction matters. A 2004 WHO expert consultation on appropriate BMI for Asian populations kept the international cut-offs above as the classifications, but found that the proportion of Asian people at high risk of type 2 diabetes and cardiovascular disease is substantial at BMIs lower than 25, and proposed 23.0, 27.5, 32.5 and 37.5 as additional public-health action points along the BMI continuum. The tool itself still shows the international categories. Whatever your result, BMI is one of several numbers a clinician weighs together with your age, family history and examination. Speak to a clinician about what your number means; this page does not give medical advice.
How it works
The result is computed entirely in the browser, from the numbers you type. In metric mode, bmi-calculator-client.tsx divides weight in kilograms by height in centimetres converted to metres, squared (bmiFromMetric); in imperial mode it converts pounds and feet-inches to the metric equivalents and applies the standard imperial factor of 703 (bmiFromImperial). The category label comes from categoryFromBmi, which applies the WHO cut-offs exactly: below 18.5 underweight, below 25 normal, below 30 overweight, and 30 or above obese. The page validates the inputs before showing anything: metric weight must be between 20 and 300 kg and height between 50 and 250 cm; imperial weight between 44 and 660 lb, height between 1 and 8 feet with 0 to 11 inches. The result appears only when the value falls between 0 and 100 and no field has a validation error, and it is displayed to one decimal place. Load Sample fills 65 kg and 170 cm. Your numbers are used only for the calculation: the weight and height you enter are not sent to a server. The analytics events the page fires record only which unit toggle you pressed and whether you loaded the sample values.
Use cases
- A health-post visitor in a rural commune who wants to understand what the height and weight reading taken by the nurse means before the referral conversation.
- A patient at a Phnom Penh clinic who wants the BMI number in hand when asking their doctor what it means for them personally.
- A job applicant who needs to fill in a BMI field on a pre-employment medical form and wants to check the arithmetic before the appointment.
- A relative in the United States who knows their weight in pounds and height in feet and inches and wants to compare their own result with family in Cambodia using the imperial mode.
- A commune health-screening volunteer who records BMI alongside other measurements during a community event and refers anyone with questions to the clinic.
- A gym member in Siem Reap who wants a number to discuss with their trainer instead of relying on an estimate from a phone app.
Frequently asked questions
Is my BMI a diagnosis?
No. BMI is a screening ratio calculated from weight and height only; it cannot measure body composition, muscle mass, fat distribution, blood pressure, blood sugar or any other health marker. A category such as overweight or obesity is a statistical band, not a verdict on you as a person. Only a clinician can interpret what a BMI value means for a specific individual, so discuss your number with one.
Why does this calculator not use the lower Asian thresholds some sources mention?
The tool implements the international WHO categories: below 18.5, 18.5 to 24.9, 25.0 to 29.9, and 30.0 or above. The 2004 WHO expert consultation on Asian populations deliberately retained those international classifications and proposed 23.0, 27.5, 32.5 and 37.5 kg/m² only as additional public-health action points, because the BMI cut-off for observed risk varies from 22 to 25 between different Asian populations. Whether any population-specific consideration applies to you is a question for a clinician, not a website.
Does a "normal" result mean I am healthy?
No. The normal band (18.5 to 24.9) describes where the ratio falls among the WHO adult categories; it does not measure fitness, blood pressure, blood sugar, cholesterol or any other marker of health, and it does not account for muscle mass or age. BMI is one screening number among many, and no category is a personal failing. If you have health concerns, a clinician is the right person to discuss them with, whatever the number says.
Can I use this calculator for a child?
No. The categories implemented here are the WHO adult classifications. For children and adolescents, overweight and obesity are defined against age- and sex-specific WHO growth references, which this tool does not implement. Ask a health facility that measures children to interpret a child's height and weight.
What weight and height ranges does the calculator accept?
In metric mode, weight must be between 20 and 300 kg and height between 50 and 250 cm. In imperial mode, weight must be between 44 and 660 lb, height between 1 and 8 feet, plus 0 to 11 inches. Values outside those ranges are rejected by the form validation before any result is shown.
Do the numbers I enter leave my device?
No. The calculation runs entirely in the browser from the values you type, and the weight and height are not sent to a server. The only analytics events the page fires record which unit system you chose and whether you pressed Load Sample; they carry no measurement values.
Is this page an official health service?
No. This is a calculator that applies the WHO adult BMI categories to the numbers you enter. It is not a medical device, it does not issue diagnoses, and it is not affiliated with any clinic or ministry. For anything that affects your health decisions, speak to a clinician.
Data and accuracy
The categories follow the World Health Organization adult BMI classification — underweight below 18.5, normal 18.5–24.9, overweight 25.0–29.9, obesity 30.0 and above — as stated in the WHO fact sheet on obesity and overweight and in the WHO Global Health Observatory BMI indicators. The Asian-population note follows the 2004 WHO expert consultation published in The Lancet, which retained the international cut-offs and proposed 23.0, 27.5, 32.5 and 37.5 kg/m² as additional public-health action points along the BMI continuum. The calculation itself runs locally in the browser; no external data is fetched, so there is nothing to refresh.
Sources
- WHO — Obesity and overweight (fact sheet, updated 7 October 2026) — World Health Organization
- WHO Global Health Observatory — Body mass index (BMI) indicators — World Health Organization
- Appropriate body-mass index for Asian populations and its implications for policy and intervention strategies (WHO Expert Consultation, The Lancet 2004) — Elsevier (The Lancet)
Content last reviewed 19 October 2026