Sizing - Trainers

All measurements are approximate - You want them stretched a bit to stay on. 
Size Waist

Wool ones, add another 1" for stretchiness

Hip
9-18m 13-15.5” / 33-40cm 15” / 38cm
2T 14.5-18” / 37-46cm 16” / 40cm
3T 15-19” / 38-48cm 17” / 43cm
4T 16-21” / 40-53cm 18.5” / 47cm