I don't know about Sidi's shoe sizer but I wear a 46 Dominator, which should be a 11.25" or a size 12. The shoes fit nicely and feel great. When I began shopping for shoes I tried on 44's, which should have fit but didn't. So, the chart may or may not be a useful tool but be sure to try on shoes before buying a pair. Just because they're your size doesn't mean they'll fit you.