You will need 4 buttons, approximately 3/4 (19 mm).

Finished measurements:
Cardigan is shown in short and long sleeve lengths.
Chest circumference: 16.5(17.75, 18.5, 19.25, 20, 21)“ 42 ( 45, 47, 49, 51, 53) cm
Finished length: 10.75( 11, 12, 13, 13.75, 14.5)” 26( 28/, 31, 33, 35, 37) cm
Long Sleeve seam: 10.75( 11, 12, 13, 13.75, 14.5)“ 26( 28, 31, 33, 35, 37) cm
Short Sleeve seam: 2’ (5 cm) for all sizes

Yarn used:
Sirdar Snuggly
Long Sleeve version
A. 531 Marmalade - 1 ball for all sizes
B. 525 Meadow - 1(1, 1, 1, 1, 2) balls
C. 533 Piglet - 1 ball for all sizes
D. 251 White - 1 ball for all sizes

Short sleeve version
A. 251 White - 1 ball for all sizes
B. 533 Piglet - 1 ball for all sizes
C. 526 Buttercup - 1 ball for all sizes
D. 534 Paddle - 1 ball for all sizes