Um so weird question,i actually had a problem recently where a condom actually squeezed me so tight i went soft,just wondering whats the best to buy,im not incredibly large only about 4.8" girth,so you can imagine my surprise when this happened
I had the same issue, even large size condoms would fight the erection quite a bit.
I now order my condoms from "my one fit" they have something like 60 different sizes, and they'll send you free sample packs ($2 shipping) to try the size you selected by entering your measurements on the website.
You should be able to fit standard condoms. From personal experience.
5.25"-6" Magnum XL
Magnums aren't much bigger in circumference than standard condoms, just longer.