NEED HELP CHOOSING A SIZE FOR MY CLIMBING SHOE

I'm interested in ordering the La Sportiva Katana Lace but am unsure about what size to get. Street size shoe is 12. Right now I'm wearing a La Sportiva Oxygym (straps) size 45 1/2 WITH SOCKS and it's tight. (The reason I wear with socks is because ordered too big and couldn't return. Don't want to make the same mistake.) What size should I order? Appreciate the help.

43.5 if you want them tight. 44 for all day.

Best thing would be to hit a climbing shop and get fit for shoes.