At 45kg the BMI runs from 20.0 at 150cm to 11.3 at two metres — a spread of nearly nine points from a single unchanged weight. So the useful question is not what BMI this weight gives, which is unanswerable, but which heights it suits. Inverting the formula: the healthy band of 18.5 to 24.9 corresponds to heights betw..
= 5ft 8.9in
YOUR RESULTS
BODY MASS INDEX
14.7
Severely Underweight
BMI PRIME
0.59
Normal = 0.74–1.00
PONDERAL INDEX
8.4
kg/m³
HEALTHY WEIGHT RANGE
56.7 – 76.3 kg
Gain 11.7 kg to reach healthy weight
Significantly below a healthy weight. Medical attention recommended.
BMI GAUGE
YOUR POSITION
FULL SUMMARY
WHO BMI CATEGORIES
The weight is already set to 45kg, which is about 99 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 45kg the healthy band runs 134 to 156cm, 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 45kg — about 99 pounds — the BMI is undetermined until a height is supplied. At 150cm it is 20.0, at 175cm 14.7, and at 200cm 11.3: a spread of 8.8 points from one unchanged weight, which is wider than the entire healthy band. Inverting the formula gives what a weight can determine: 45kg sits inside the healthy BMI band for heights between 134cm and 156cm, a window 22cm wide, or roughly 4ft 5in to 5ft 1in. On the WHO 2004 cut-offs for South and East Asian populations the shortest suitable height rises to 140cm, 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.