Recommended Sizing Method
Place a blank piece of paper flat on the ground, against the edge of a wall. Stand barefoot on the paper, with your heel to the wall. Since it is important to stand up straight, preferably have someone help you draw a line in front of the longest toe. Remember to measure both feet as they might not be identical. With a ruler, measure the distance from the edge of the paper to the mark and add additional space according to the list below.
Additional space
Skiing boots
Note that this method is purely intended as a guideline. Below is Scarpa's own recommendations.
SCARPA ski boots break on the half size, this means that a half size shares the same shell length as the whole size above it but the liners are lasted for each 1/2 size. For example, a 25.5 and 26.0 are the same shell size but the respective liners come pre-molded to the half size.
Some skiers may want to downsize up to 1 full Mondo size, depending upon personal preference.