Depending on how many words you would like to have on the cross will determine the size.
‘god bless eve sophia’ is a medium size. ‘imogen rose’ is a small size.
small 12 x 9.6 cm, drop length 30 cm approx
medium 17.5 x 13 cm, overall drop length 40 cm
large 24.5 x 19 cm, overall drop length 45 cm