for that size i usually do 65-70" x fabric width or sometimes a tad longer and wider if they are taller than usual
ETA: for a 3 yo (i didn't see earlier sorry) i usually do 60xfabric width. so it's not super heavy but they don't outgrow it super quick either
Last edited by Austinite; 01-25-2018 at 04:45 PM.