Check out this ponderal index calculator if you’re seeking a more precise measure than the BMI. The ponderal index, also known as the corpulence index or Rohrer’s index, can help you determine if you’re overweight, underweight, or just right, similar to how the BMI score can. However, because PI has greater sensitivity and specificity, if you are tall, your BMI may indicate that you are fat, but this is not always the case. In pediatrics, the infant ponderal index is used to determine if a newborn baby is malnourished, healthy, or overweight, as well as in disorders like intrauterine growth restriction, in which the child grows poorly in the mother’s womb. Continue reading to learn more about ponderal index formulae and normal ranges.
Ponderal index formula
BMI = weight / height²
whereas ponderal index use height³ – which makes more sense as our bodies are 3-dimensional structures, not 2D!
PI = weight / height³
BMI works well for persons of medium height (about 5 ft 6 in / 170 cm), but if you are really tall, your BMI number will almost certainly imply obesity. If you’re short, BMI can help you maintain a healthy weight, even if you need to reduce a few pounds.
In PI calculations for adults, the fundamental weight unit is kg, while height is measured in meters. Weight is normally given in grams and height is given in cm for newborns and newborn babies:
PI_adult = weight [kg]/ height [m]³
PI_child = weight [g]/ height [cm]³ = 0.1 * PI_adult
Ponderal index normal range
The ponderal index of an adult is 12 and that of a newborn kid or infant is 2.4 (24) for a normal or typical value. The usual ranges of the ponderal index are also defined as follows:
- 11 – 15 for adults – values derived from BMI for the reference height of 170 cm; sometimes 11 – 14 range is used
- 2.2 – 3.0 for newborn babies – simplified, generalized normal PI range, irrespective of weeks of gestation, child’s sex and maternal parity
BMI and PI aren’t ideal measurements because they don’t distinguish between muscle and fat. The BMI or PI of a strong athlete and an overweight man might be the same. Keep in mind that your PI is only an indication, not an exact assessment of your health.
Use our body fat calculator to figure out what percentage of your total body weight is made up of fat, and our lean body mass calculator to figure out how much you’d weigh if you weren’t fat. If you’re on a diet or starting an exercise regimen to get a leaner physique, you might find the following tools useful:
- BMR calculator – to find out how many calories you burn every day when you rest for the whole day
- Ideal weight calculator – to check ideal weight for you
- Calorie calculator – to figure out how many calories a day you need – and how many to cut if you want to lose weight
- Heart rate calculator – to determine the heart rate you should aim for when performing a certain intensity of exercise
Infant ponderal index
The infant ponderal index is used to determine whether newborns are underweight, normal weight, or overweight. It’s also one of the anthropometric tools for diagnosing fetal growth problems. It aids in determining if a child’s intrauterine growth restriction is symmetrical (normal PI) or asymmetrical (abnormal PI) (low PI).
The value of PI for the infant is presented in our calculator. We do not, however, assess its nutritional condition because it is determined by other factors such as gestational age, neonatal sex, and maternal parity. If you’re interested in learning more about the relationship between PI and those metrics, check out this article on the neonatal ponderal index.
Ponderal index calculator – how to use
If you’re still stumped on how to calculate the ponderal index, follow this step-by-step guide:
- Choose the person for whom you want to do the calculations. Select an infant or an adult. Let’s assume we want to calculate the PI for a grown-up, so the ponderal index formula for an adult will be used.
- Enter the person’s height. Assume it’s 6 feet. You can change the units by a simple click of the unit’s name.
- Type the weight. For example, 195 lb.
- Corpulence index is displayed as well as the information about your body. In our case, it equals 13.97 which gives a normal, healthy range.
check our other calculator:
- General BMI calculator
- BMI calculator for kids
- BMI calculator for teenagers
- BMI calculator for women