Gauge:
22 sts + 19 rows = 4” in Body pat with larger needles
22 sts + 28 rows = 4” in stockinette stitch with larger needles

Size: 12, 18, 24 months
Waist: 20, 21.5, 22”
Length: 17, 19, 21”

Total yarn required for pants and matching Kimono which can be found here is:
MC: 920, 920, 1380 yards (825, 825, 1240 m)
CC: 450 yards (415 m)