BMI Prime & Target Weight Calculator
Calculate your BMI Prime (BMI relative to the 25 upper limit), see your category, and find the weight that brings you to a healthy BMI.
How it works
BMI = weight(kg) ÷ height(m)² · BMI Prime = BMI ÷ 25 · weight at Prime 1.0 = 25 × height(m)²
BMI Prime rescales body mass index against the 25 upper limit of the healthy range, so a value of exactly 1.0 sits right at that boundary. It turns BMI into an at-a-glance ratio: 1.15 means you are 15% above the top of the healthy band, while 0.9 means 10% below it. Because it is dimensionless it also makes it easy to compare populations with different average heights.
Worked example
Someone 175 cm and 80 kg has a BMI of 80 ÷ 1.75² = 26.1, giving a BMI Prime of 26.1 ÷ 25 = 1.05 — overweight, 5% above the limit. The top of the healthy range for 175 cm is 25 × 1.75² = 76.6 kg, about 3.4 kg below their current weight.
Sources: BMI Prime (definition)
Frequently asked questions
What is a normal BMI Prime?
A BMI Prime between 0.74 and 1.0 corresponds to the normal BMI range of 18.5–25. Below 0.74 is underweight, 1.0–1.2 is overweight and above 1.2 is obese.
How is BMI Prime more useful than plain BMI?
It expresses your BMI directly as a fraction of the healthy upper limit, so 1.1 immediately reads as "10% over". That makes progress and comparisons easier to interpret than a raw kg/m² figure.
Does BMI Prime share BMI’s limitations?
Yes. Like BMI it does not distinguish muscle from fat or account for body-fat distribution, so very muscular people can score high without excess fat. Use it as a screening ratio, not a diagnosis.
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Educational estimate only — not medical advice. Individual needs vary; consult a qualified professional before making health decisions.