So I got a set of Continental Touring Plus tires last night, in size 32-622

They seemed smaller than my previous 32-622s so I busted out my crescent wrench.

Actual measurement? 26-622. WTF??

I mean, they rode fine at max PSI (80) on the way in this morning, but seriously? Almost 20% thinner than the label indicates?

All of the Continental tires I have bought have been narrower than the nominal size, although mine have all been racing tires. Eg., my Conti GP 4000 in size 700 x 25 measure closer to 23 or 24 mm wide. However, this is not unusual among tire manufacturers, for some reason. Maybe they are measuring the height of the tire rather than the width?

What is odd is that Michelins use to run wider than their nominal sizes. I've got some Michelin Pro2Race and Carbons in size 25 that actually measured 27-28 mm wide. However, I have heard that the new Michelins run narrow, like most other brands, since they moved production to Thailand.

Eh, tire manufacturer sizes vary. That applies to car tires, bike tires, and just about everything in life. It's a comparison, not an exact size.

Also, I measured a 2x4 I got from Home Depot last weekend... IT'S NOT EVEN A FULL TWO INCHES.

While I agree with tarwheel that Conti tires are usually thinner than listed (my 28mm Gatorskins measure up at 26.8mm on a DT RR1.1 rim), that's only a 4.3% difference, not 20%.
I'm thinking that some of the issue may be due to the imprecise measurement equipment. Measure them with a calibrated caliper and I'm willing to bet you get a measurement closer to 29mm.

I suppose the measurement could be flawed.
My crescent wrench has milimeters on it indicating how wide open it is. I used it to measure my previous set of 32-622 Panaracer Urban Max and they were 32mm on the nose.

...so even if flawed it was a controlled experiment at least!!

Same here. I used several Conti models, and they all seemed a little undersized. But a little - not 26 instead of 32. 4 seasons I have on now measure 27mm, even though the label says 28.

Others may know more though.