Infant and toddler clothing size is typically based on age. These are usually preemie for a preterm birth baby, 0 to 3 months, 3 to 6 months, 6 to 9 months, 9 to 12 months, 12 months, 18 months, and 24 months, though there is no industry standard definition for those sizes. Most retailers provide sizing charts based on a child's weight, height, or both, and the child's weight and height percentile may also be used for properly sizing clothing for the infant.