Measurements (chest measured pit to pit):
3/4 (Chest 36cm, Sleeve 38cm, Neck to Crotch 52cm and Inseam 38cm),
5/6 years (Chest 40cm, sleeve 43cm, Neck to Crotch 56.5cm and Inseam 45cm),
7/8 years (Chest 44cm, Sleeve 48cm, Neck to Crotch 61.5cm and Inseam 52cm),
9/11 years (Chest 48cm, Sleeve 53cm, Neck to Crotch 69.5cm and Inseam 59cm),
12/13 years (Chest 50cm, Sleeve 58cm, Neck to Crotch 77cm and Inseam 66cm)
Please note that there can be a 1-2cm difference give or take but these are onesies and are designed to be a little baggy compared to other styles of garment.