Children's shoes come in several categories. To convert women's shoe sizes to kids' sizes, you'll most likely be looking in the youth or big kids' shoe sizes. The tiniest women's shoes (smaller than size 4) may be converted into little kids' sizes. Women's and children's shoe sizes are labeled differently in the United States, the United Kingdom and throughout the rest of Europe. While European sizes are generally standard -- a European size 36 is the same for women and kids -- U.S. and U.K. sizes differ slightly between women and children.
If You Know Your Shoe Size
Check the size of your best-fitting women's shoe. This size will be marked in U.S., U.K. or European measurements. If the shoe is in European measurements, no conversion is necessary.
Find the number of inches that corresponds to your shoe size on a shoe-size chart. If your women's shoe is a U.S. size 7, for example, your foot is 9.25 inches in length.
Find your foot length under the kid's size section of a shoe-size chart. If your exact length is not provided, round up to the nearest length, which will be within 1/16th of an inch. For example, a 9.25-inch foot is a U.S. women's size 7, a U.K. women's size 5, a U.S. child's size 5.5, and a U.K. child's size 4.5, according to a shoe-size chart.
If You Don't Know Your Shoe Size
Place your foot flat on a sheet of paper that is larger than your foot from heel to toe. You should be wearing the socks you plan to wear with your shoes to ensure a proper fit.
Secure the paper to the floor or to a firm, sturdy surface -- such as a large book -- with masking tape at the corners of the paper.
Hold a pencil perpendicular to the paper, with the eraser pointing toward the ceiling. Trace the entire outline of your foot.
Locate the highest point of your longest toe. Use your ruler and pencil to draw a straight line across the paper at this point, perpendicular to the length of your foot. This way, you'll measure your foot outline at its greatest length. Draw another straight line at the back of your heel.
Measure the distance between your two straight lines to the nearest 1/16th of an inch (0.0625 in). When in doubt, round up to the next largest measurement. Measure both feet and use the measurement of the largest foot to find your size.
Match the length of your foot to the corresponding women's and kid's shoe size according to a shoe-size chart. If your foot length is not listed with a corresponding size, add 1/16th of an inch (0.0625 inches) to your foot length. For example, if your foot length is 9.0625 inches, or a U.S. women's size 6.5, there is no corresponding child's shoe size in that length. In that case, round the length up to 9.125 inches, which would be a U.S. child's size 5.