First,you need to measure your foot length ,next,please according to your foot length to choose shoe size.
EUR 39= Foot Length 24.5cm=US Size 7.0;
EUR 40= Foot Length 25.0cm=US Size 7.5;
EUR 41= Foot Length 25.5cm=US Size 8.0;
EUR 42= Foot Length 26.0cm=US Size 8.5;
EUR 43= Foot Length 26.5cm=US Size 9.0;
EUR 44= Foot Length 27.0cm=US Size 9.5;
EUR 45= Foot Length 27.5cm=US Size 10.0;
EUR 46= Foot Length 28.0cm=US Size 10.5;
EUR 47= Foot Length 28.5cm=US Size 11.0;
EUR 48= Foot Length 29.0cm=US Size 11.5;