Every Pretty Little Prop Headband is designed so they are stretchy this way the headband will fit perfectly.
Sizing doesn't have to be so specific because you can re-tie to suit you
Sizing Guide,
Newborn is 12 inches
Toddler is 14 inches
4-10 is 17 inches
10- teen - 19 inches
Wash at 30/delicate wash, do not tumble dry.