The shoes that fit perfectly in earlier adulthood often become uncomfortable later in life. The simple answer to whether shoe size changes is a definitive yes. Shoe size indicates the fitting size of a shoe, based on the length and width of the foot itself. Changes to foot size are frequent throughout a person’s life, driven by development, physiological events, and the mechanical wear of daily living.
Changes Driven by Development and Age
The most rapid changes in foot size occur during childhood and adolescence. A baby’s foot contains more cartilage than bone, and the bones do not fully harden until around age 13. Children’s feet can grow by as much as a half-size every two to four months during infancy, slowing down after age six.
Once skeletal maturity is reached in late adolescence, the feet stop getting longer, but changes continue. Over decades, the continuous impact of gravity and body weight causes the ligaments and tendons supporting the arch to gradually lose elasticity and strength. This process leads to a flattening and spreading of the foot structure.
As the arch collapses, the foot lengthens and widens, potentially increasing shoe size by a half to a full size over an adult lifetime. The loss of elasticity allows the foot to pronate more, meaning the arch lowers and the foot rolls inward. This structural alteration means that shoes worn in one’s twenties may become uncomfortably tight in middle age.
Hormonal and Weight-Related Factors
Specific physiological events, beyond general aging, can cause abrupt changes to foot size. Pregnancy is a notable example, involving a surge of hormones, particularly relaxin, released to prepare the body for childbirth. While relaxin primarily increases the elasticity of ligaments in the pelvis, it affects ligaments throughout the entire body, including those in the feet.
The resulting ligamentous laxity allows the arch to flatten and widen under the increased body weight of pregnancy. This change is often permanent, leaving many women with a larger foot size after giving birth. Significant fluctuations in body weight also directly impact the feet, which bear the entire load of the body.
Substantial weight gain increases mechanical stress, compressing the fat pads and forcing the arch to flatten, which increases the foot’s length and width. While significant weight loss can reduce swelling, it rarely reverses the structural changes caused by years of arch flattening. The thinning of the fat pads on the soles of the feet, a common change with age, also alters how a shoe fits by reducing natural cushioning.
The Difference Between Foot Size and Shoe Size
Many people attribute a poor shoe fit to a change in size when the issue is often a mismatch between the foot’s actual dimensions and the shoe’s internal shape. A shoe size is an arbitrary number assigned to the shoe’s internal cavity, designed to accommodate a foot of a certain length and width. Because there is no global standard, the same size number can vary significantly between different shoe brands and models.
It is important to measure feet regularly, even in adulthood, to ensure the best fit. Foot dimensions fluctuate throughout the day due to gravity, often swelling by the evening, making a late-day measurement more accurate for purchasing new footwear. Since one foot is commonly slightly larger than the other, shoes should always be purchased to fit the larger foot.
Changes in size often involve width more than length, yet many individuals wear the wrong width because they focus only on the length number. Using a proper measuring device, such as a Brannock device, provides both length and width measurements crucial for a comfortable fit. Prioritizing how a shoe feels over the size number printed on the box is the most practical advice for foot health.