Adults generally get used to the fact that their feet don’t change sizes, which means they can buy shoes that are always the same size and wear them until they fall apart. Parents are often astounded to realize their child’s feet don’t work that way. Their feet are constantly growing and developing, and you need to keep buying them shoes even though their old shoes are in great shape. They just don’t fit anymore.
The baby to toddler transition period is when the feet grow the fastest. They can grow a half shoe size every two months until they hit age 15 months. During this period, their feet also change dramatically in shape, beginning to develop a defined arch and a heel, and elongating. Generally babies don’t need shoes and their feet develop more normally if they just wear socks for warmth if needed.
During the toddler phase, the child’s feet continue to grow and develop at an alarmingly fast rate, increasing by about a half shoe size every three to four months, but gradually slowing down as they approach age three. It’s best to avoid stiff, restrictive shoes with elevated heels during this period and let the little one go barefoot or just wear some kind of soft, unstructured protective foot covering.
Children in the three to five years old range will go up a half shoe size every four to five months. Children in this age group are generally quite active and fully able to run and walk on their own, and will need shoes. A lot of shoes since they will outgrow them rapidly; generally, they need a new pair of shoes every four months. Letting them go barefoot as much as possible is definitely a healthy option.
Foot growth between age five and puberty gradually slows down, but also becomes less predictable and more variable among different children. Some children will have the same shoe size for an extended period and then suddenly hit a growth spurt, while others will just steadily and predictably outgrow their shoes every six months.
After puberty, most but not all girls will achieve their adult foot size and structure by age 14, and similarly most but not all boys will do the same by age 16. Some individuals experience growth spurts well into their teenage years, but generally everyone can be assumed to fully physical mature by age 25.