Salomon also use the Mondopoint measuring system which helps...
Its metric basically. Measure your feet and round it up or down to the nearest 5mm
So a 29.5cm foot = 29.5 mondopoint boot. Caters for + and - 2.5mm
If ur on the cusp id say go a size down because the boots will fill out n then you'll still have a good hold when theyre fully broken in