Joined: Jan 2010
Posts: 9,835
Likes: 1,816
From: Northern California
Bikes: Cheltenham-Pedersen racer, Boulder F/S Paris-Roubaix, Varsity racer, '52 Christophe, '62 Continental, '92 Merckx, '75 Limongi, '76 Presto, '72 Gitane SC, '71 Schwinn SS, etc.
Yeah, the labeling is kind of casual when viewed by the consumer.
One thing to know about comparing tubes is that the most accurate width measurement will be made with the airless tube flattened, then you can add 10 or 20% to that figure to know what the largest size tire (actual inflated size of tire) that is still safe.
Or, you could do like I do and put a flat-measured 26mm tube (labeled 20-28mm / 1-1/8") into your 23mm tires, for a slower loss of air when you puncture.
Most "standard road" (racing) tubes, the narrowest tubes available, will measure 22-26mm wide flat.
These will have labels ranging from 700X20 to 700X28, which may or may not correspond to the comparative width of the labeled tube.
Believe it or not, I've been sent batches of tires which were all of the same size yet bore slightly different size labeling, with some even having two different size designations on the same tire (one printed on, the other molded in raised letters)!!!
It's a jungle out there.