As a very general guideline, here are the average bracelet sizes for children:
NewBorn - 4 inches
3-6 Month - 4.5 inches
7-12 Month - 4.75 inches
12-24 Month - 5 inches
2 Years - 5.25 inches
3 Years - 5.5 inches
4-5 Years - 5.75 inches
6-7 Years - 6 inches
8-9 Years - 6.25 inches
10-11 Years -6.5 inches
12-13 Years - 6.75 inches
14 Years to Young Adult - 7 inches
Of course, all children are different so it's best to measure the wrist of the child and go from there. If you are making a beaded (strung) bracelet, adding an extender chain will give them some growing room.
Here's how to make a child's bracelet measurement: Measure the child's wrist, then add about a 1/4 inch for small sized beads, and about a half inch for medium sized beads. If you need a really accurate sizing for the bracelet, you might want to use a bracelet measuring tool like the one I made here.
