Growth velocity, or the speed at which something or someone is growing, is often tracked for children. Growth can be measured in length, such as the length of the body or even of one limb, or in overall weight. The velocity aspect of the measurement refers to the change over time. So calculating growth velocity is a simple matter of measuring a child's weight or height at two points in time and then dividing the change by the amount of time. The concept of growth velocity is not limited to the growth of a person, but could be applied as well to the growth of an animal, plant, population or even an investment.
Take the first measurement of a child's height or weight. For instance, suppose you measure your baby's weight at birth, and it is 7 lbs. and 6 oz.
Wait a certain amount of time and take a second measurement to see how much the child's height or weight has changed. For instance, suppose at 6 days old, your baby weighs 7 lbs. and 11 oz.
Subtract the initial measurement from the final measurement to calculate the chance in height or weight. In the example, your baby's weight changed by:
7 lbs. - 7 lbs. = 0 lbs. and 11 oz. - 6 oz. = 5 oz.
So the baby's weight changed by 5 oz.
Divide the change in height or weight by the amount of time over which the change took place to calculate the growth velocity. In the example, it took six days for the baby to gain 5 oz. So the growth velocity = 5 oz. / 6 days = 0.83 oz. per day.