I'm guessing on exact sizes, but the "shoebox" containers they're in seem to be around 14"L x 8"D x 5"H. The snakes are all right around 14"-16". (I don't own a tape measure, so I'm using standard 8.5"x11" notebook paper as a ruler right now. My numbers might be a little off.) I had been thinking about getting a taller box for Kismet, since she seems to be a climber, but the other two haven't yet left the ground level.
@Marike: Thanks for the formula! It's good to have a solid numerical idea for how big they should be. So by Germany's standards, they're already too big for these containers. Wow 0.o They seem so tiny in there. Is that echoed by opinions elsewhere in the world?
I'm a little bit low on money right now, so I can't upgrade to anything larger for a month or two (dog vet bills = expensive). Should mine be okay in containers of that size for the time? I can get pictures if anyone wants a visual.
I do have one 10-gallon tank that isn't being used right now, but when I put Trinket and Pierce in there (temporarily cohabitating while I was trying to find other containers), they seemed really nervous about the large-ness of it. It was also previously used for rodents. I've washed it pretty thoroughly since then, but I wasn't sure if the smell would aggravate them...
I also have what are currently my yarn drawers (stackable clear tubs), which are a fair bit bigger than the shoe-box size. I'd say probably 16"L x 6"H x 12"D. I only have two of those, though, and I don't know how I'd attach an UTH to it without making one of the drawers stick open slightly, which means a corn might be able to squeeze out.
Actually, now that I think about it, I have three huge storage bins that I used for moving. They're not clear, so I'd have to open the container every time I wanted to look at/play with them, and I'd have to contrive some sort of lid that would let light in (boxes are opaque blue plastic), but that's a doable option once they outgrow the current containers.