Design E and pattern leaflet also include instructions to knit this as a tank top/vest (separate Ravelry entry here)

Sizes: to fit chest / actual measurements
2-3 yrs (chest size 22”/56cm) / (24.5”/62cm)
4-5 yrs (chest size 24”/61cm) / (26”/66cm)
6-7 yrs (chest size 26”/66cm) / (27.5”/70cm)
8-9 yrs (chest size 28”/71cm) / (30”/76cm)
10-11 yrs (chest size 30”/76cm) / (31.5”/80cm)
12-13 yrs (chest size 32”/81cm) / (34”/86cm)

Yarn Requirements: Aran weight, 100g balls
MC: 2 (2, 3, 3, 4, 4) balls
CC: 1 ball all sizes

Sirdar: http://www.sirdar.co.uk/designs/children/sweatersChildren...