Instantly see how far your weight is from the healthy range
Your Measurements
Your BMI Prime Result
BMI 18.5 – 24.9. Associated with the lowest health risks for most adults.
BMI Prime Scale
How BMI Prime Works
BMI Prime normalises BMI against the upper boundary of the normal range (BMI 25). A BMI Prime of 1.00 exactly equals BMI 25; values below 1.00 are at or below the upper normal limit, and values above 1.00 exceed it. This makes it easy to compare across different weight thresholds: a BMI Prime of 1.20 means a person is 20% above the upper boundary of the normal range.
BMI Prime Reference Table
| BMI Prime | BMI Range | Category |
|---|---|---|
| < 0.74 | < 18.5 | Underweight |
| 0.74 – 1.00 | 18.5 – 25 | Normal Weight |
| 1.00 – 1.20 | 25 – 30 | Overweight |
| 1.20 – 1.40 | 30 – 35 | Obese Class I |
| 1.40 – 1.60 | 35 – 40 | Obese Class II |
| > 1.60 | > 40 | Obese Class III |
Note: BMI Prime and BMI are screening tools, not clinical diagnoses. They do not account for muscle mass, bone density, fat distribution, age, sex, or ethnicity. Always consult a qualified healthcare professional for personalised medical advice.
BMI Prime is a simple ratio — your BMI divided by 25 — that instantly tells you how your weight compares to the upper boundary of the healthy range. A BMI Prime of 1.00 equals BMI 25; values below 1.00 are within or under the normal range. Use this free BMI Prime calculator to check your score in metric or imperial units and understand your weight category at a glance.
BMI Prime is your Body Mass Index divided by 25 (the upper limit of the normal BMI range). A score of 1.00 means your BMI is exactly 25. Scores below 1.00 are at or under the normal upper limit, while scores above 1.00 indicate you are above it. For example, a BMI Prime of 1.20 means your BMI is 30 — 20% above the healthy boundary.
First, BMI is calculated as weight in kilograms divided by height in metres squared (kg/m²). BMI Prime is then simply BMI ÷ 25. In imperial units, BMI = 703 × weight(lbs) ÷ height(inches)², and BMI Prime is still that result divided by 25.
A BMI Prime between 0.74 and 1.00 corresponds to the normal weight range (BMI 18.5 – 25) and is associated with the lowest health risks for most adults. Scores below 0.74 suggest underweight, while scores above 1.00 indicate overweight or obesity.
BMI Prime conveys the same information as BMI but in a more intuitive form. Because the reference point is always 1.00, it is easier to understand how far above or below the healthy upper limit a person sits. However, like BMI, it does not account for muscle mass, age, sex, or fat distribution, so it should be used alongside other health indicators.