SIZING CHART 

Keep in mind that different brand has differnt sizing chart. This one is for TREKSTA. The length is inside the shoe. 
Down load pdf

KIDS - COMFORT SOLE

Length (mm) 123 129 134 139 142 148 156 160
Size 20 21 22 23 24 25 26 27

KIDS - NESTFIT SOLE

Length (mm) 130 135 140 145 149 154 163 167
Size 20 21 22 23 24 25 26 27

JUNIOR

Length (mm) 172 177 187 192 196 202 210 215 221 227 234 238
Size 28 29 30 31 32 33 34 35 36 37 38 39

ADULT

Length (mm) 235 243 251 257 265 270 276 283 290 295 303 312
Size 36 37 38 39 40 41 42 43 44 45 46 47

COMFORT SOLE

NESTFIT SOLE