Knitted strap for baby bonnet 27 October 2016 at 7:20PM in Crafting

carefullycautious

I have just knitted a baby bonnet and want to put a knitted strap in garter stitch with buttonholes to attach to the buttons either side of hat. As I don't have a baby head available I am lost as to the length it should be. The bonnet round face is 12 inches.