You will need 9 buttons. rowan used #BN1564 from Bedecked in the UK.

Circumference: 39(4.25, 47.25, 51.25, 55.5)“ 99(110, 120, 130, 141) cm
Finished length: 26(26.75, 27.5, 28.25, 29.25)” 66(68, 70, 72, 74) cm
Sleeve length to underarm: 17.75(17.75, 18, 18, 18, )“ 45(45, 46, 46, 46) cm

Yarn used:
Rowan Mossdale
A. Pepper 002 - 4(5, 5, 6, 6) hanks
B. Bronzed 006 - 1 hank for all sizes.
C. Nutmeg 011 - 1 hank for all size