Measure around your knuckles (at base of fingers) and this will give you your size -
4XS: 6" (16cm), 40cm long end to end
3XS: 6.5" (17cm), 40cm long end to end
2XS: 7" (18cm), 45cm long end to end
XS: 7.5" (19cm), 45cm long end to end
SMALL: 8" (20cm), 53cm long end to end
MEDIUM: 8.5" (22cm), 55cm long end to end
LARGE: 9" (23cm), 57cm long end to end
XL: 10" (25cm), 57cm long end to end
2XL: 10.5" (27cm), 60cm long end to end
3XL: 11" (28cm), 60cm long end to end