27 1/4??? Do you mean 27 x 1 1/4?

And what do you mean by "equivalent"? You can't put a 700 tire on a 27" rim. Do you mean, what 700 rim/tire combination will give a similar ride to a 27" rim/tire combination? Then you probably just want a similar tire width. To convert from inches to millimeters, multiply by 25.4, so 1 1/4" -> 32 mm.