At 55kg the BMI runs from 24.4 at 150cm to 13.8 at two metres — a spread of 10.7 points, and the first weight on this list where the range crosses ten. Ten points of BMI is the entire distance from the bottom of the healthy band to well past the obesity threshold. So a single weight, unaccompanied by a height, carries..
= 5ft 8.9in
YOUR RESULTS
BODY MASS INDEX
18.0
Underweight
BMI PRIME
0.72
Normal = 0.74–1.00
PONDERAL INDEX
10.3
kg/m³
HEALTHY WEIGHT RANGE
56.7 – 76.3 kg
Gain 1.7 kg to reach healthy weight
Below a healthy weight range. Consider consulting a healthcare professional.
BMI GAUGE
YOUR POSITION
FULL SUMMARY
WHO BMI CATEGORIES
The weight is already set to 55kg, which is about 121 pounds. Enter your height and the BMI follows — until you do, the figure is undetermined.
Both unit systems are seeded, so switching between kilograms and pounds keeps the same weight rather than reverting to a default.
Read the band of heights rather than any single BMI. At 55kg the healthy band runs 149 to 172cm, and that band is what a weight actually determines.
A reading near a category boundary should be read as near a boundary. Most people vary by one to two kilograms across a day from food and fluid alone.
At 55kg — about 121 pounds — the BMI is undetermined until a height is supplied. At 150cm it is 24.4, at 175cm 18.0, and at 200cm 13.8: a spread of 10.7 points from one unchanged weight, which is wider than the entire healthy band. Inverting the formula gives what a weight can determine: 55kg sits inside the healthy BMI band for heights between 149cm and 172cm, a window 23cm wide, or roughly 4ft 11in to 5ft 8in. On the WHO 2004 cut-offs for South and East Asian populations the shortest suitable height rises to 155cm, because those thresholds lower the top of the BMI band while leaving 18.5 in place.
FORMULA REFERENCE TABLE
| Name | Formula | Description |
|---|---|---|
| BMI (Metric) | BMI = weight(kg) / height(m)² | Divide weight in kg by height in metres squared |
| BMI (Imperial) | BMI = 703 × weight(lbs) / height(in)² | Multiply weight in pounds by 703, divide by height in inches squared |
| Height in metres | h(m) = h(cm) / 100 | Convert centimetres to metres before squaring |
| BMI Prime | BMI Prime = BMI / 25 | Ratio of BMI to upper limit of normal (25). Values >1.00 indicate overweight |
| Ponderal Index | PI = weight(kg) / height(m)³ | More accurate than BMI for very tall or short individuals. Normal: 11–15 kg/m³ |
| Healthy weight | w = BMI × height(m)² | Rearranged BMI formula: weight(kg) for any target BMI at your height |
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Last updated: August 2, 2026 · Formula verified by EagleCalculator team · Source: WHO Global Database on Body Mass Index · Eagle-eyed accuracy for every calculation.