International children’s shoe sizes use separate measuring systems, making direct comparison impossible without a conversion chart. This lack of a universal standard requires understanding specific conversions, especially for a common size like a child’s 21.
The Specific Conversion for Size 21
The number 21 is an EU sizing designation, a standard used across continental Europe. This size corresponds to a foot length of approximately 12.5 to 13 centimeters. The age range for a child wearing an EU size 21 is generally between 12 and 24 months, though foot growth rates vary significantly.
When converting this measurement, EU size 21 translates to a US Toddler size 5 or 5.5 C. In the United Kingdom, the equivalent is generally a UK Infant/Toddler size 4 or 4.5.
Decoding Global Sizing Systems
The disparity in sizing numbers lies in the mathematical basis of each system. The European system is the most uniform, based on the “Paris point,” a fixed unit equal to two-thirds of a centimeter (6.67 millimeters). This metric-based scale progresses by 6.67 mm for every full size and is used for children and adults alike.
In contrast, the UK system is rooted in the historical “barleycorn,” which is one-third of an inch (8.47 millimeters). Full sizes in the UK system increase by one barleycorn. The children’s size scale starts at a zero point equivalent to a four-inch foot length.
The United States sizing system is derived from the UK’s barleycorn measurement but uses a different starting point, or zero-point. This offset means the US size number is typically one to one-and-a-half sizes larger than the UK equivalent for the same foot length. The US system also uses separate scales for children, men, and women.
Measuring a Child’s Foot Accurately
The most reliable approach is to first measure the child’s foot length in centimeters. Have the child stand up straight with their full weight distributed on a piece of paper placed on a hard, flat surface. Ensure the heel is firmly against a wall or straight edge to establish a precise starting point.
Using a pencil held upright, mark the tip of the longest toe. Measure the distance between the wall and the toe mark in millimeters or centimeters, using the measurement from the longer of the two feet.
Add an allowance of approximately 1 to 1.3 centimeters to the measured length. This addition accounts for necessary space for toe movement and growth, as a toddler’s foot can grow by a half-size every few months. Measuring later in the day is also recommended, since feet naturally swell and are at their largest in the afternoon or evening.