Needles needed:
12mm needles, a US17 is closest at 12.75mm
10mm needles, US15

Sizes (by UK dress size):
10 - to fit bust 32”/81cm; actual size 28.25”/72cm
12 - to fit bust 34”/86cm; actual size 31.5”/80cm
14 - to fit bust 36”/91cm; actual size 33”/84cm
16 - to fit bust 38”/97cm; actual size 36.25”/92cm
18 - to fit bust 40”/102cm; actual size 37.75”/96cm
20 - to fit bust 42”/107cm; actual size 39.5”/100cm

Yarn Requirements: Ribbon yarn, 50g
Sweater: 12 (13, 13, 14, 15, 16) balls