27x1 1/8" is about 1/2" bigger in diameter than 700x23's

the ERTO of a 27" rim I believe is usually around 630mm, 700c's its around 622mm, check aebike.com's rim section, it will have the ERTO #'s listed, plus you have to factor in that the wheel sizes are with the tires mounted based on certain sizes, bike tires are usually square..........width=height or profile is usually 100% if you want to look at it that way