I made sweatpants for my 18 month old grandson, Gavin.
The last pair I made for him were too long, so I measured the pants he was wearing.
These were the measurements:
inseam 12-1/4 inches
outseam 17-3/4 inches
For these pants I used Angel Hickman Peterson’s Fleece Fun Easy Pants Pattern
Waist elastic-18" long by 3/4" wide.
Bottom leg elastic-7-3/4" long by 1/2" wide.
I straight stitched the casings for the waistline-1-1/2 inches turned over
and leg bottom-1 inch turned over.