XL Twin top and bottom. It's what colleges use for student beds these days. Just say No to mattresses on the ground.

full over full if you have the room.

for growing and sleep overs...

I might do one of each for flexibility

The bunks won't be that comfortable for teens that might grow to their full height early on and will feel crammed trying to sleep in the lower bunk.

If you have the space, get two XL twin beds (not bunks). Bunks seem like a great space saver but they aren't very user friendly, especially the top bunk. It's a pain to change the sheets for both, the top bunk can get hot, ceiling fans can pose problems and if someone isn't feeling well, climbing up and down the ladder isn't fun.

Twin beds can accommodate adult guests and styles are available with storage or trundles underneath if needed.

As stated below, XL twins are what you get in college (and a king size bed is basically 2 twins) so anything bigger than a twin is more space than you'll ever have in your life if you ever have a partner. I agree with below, though, that bunks are not so adult friendly so it depends on how long you expect to have them over for sleepovers.

XL twin beds without footboards. My family - not me - are very tall and the grands are heading that way as well. 2 grandkids have bunks and I just don’t like them for all the reasons mentioned above. Also if you have other guest couples you can move beds together , add a “thing” ( not sure what it’s called to cover the gap between the beds.

I’m still thinking of 3 XL twin beds (not bunks) but once I opened my big mouth and told them that we were making a bunk bed camping room they all got so excited. I am going to buy those bunk bed zipper comforters to make it easier. We have 5 bedrooms so we have 3 other guest rooms. Room is 13 x 14. Not huge not small. Still have a lot of deciding to do! Thanks for the advice!!

No space for a trundle? It will be a sofa style during the day.

https://www.pbteen.com/products/bailey-daybed/?group=1&sku=6776236

A lot of wooden bunks can turn into separate twin beds. We have a set that we split up when the kids stopped sharing a room. That gives you flexibility. When the beds were bunked, we used fitted sheets and then a duvet in a twin cover (IKEA has lots of good kid friendly cotton duvets) without a top sheet. that makes it easy to make the bed and is easy to wash.

If they’re young, even with memories like steel traps, could still back out of the bunk beds plan and maybe set up an indoor tent, or those tents that fit on the bed.
My grandchildren also for a time had the stacking bunk beds that were later used as 2 twins. Don’t think they were XL, though.

Bunk beds are so difficult to make and change the sheets.. Twin XL trundles are available.

I’m not really a fan of trundles or day beds. But thanks! Still thinking of not doing bunk beds now. I’m getting ready to empty and paint this room. Then we are replacing flooring so I have a little while to think about it! I want it all done in the next couple of months.

XL if the people in the kids' families are tall, particularly if the kids are boys. A regular twin will be just fine for a girl who is taller than average, but not a huge amount taller. You don't need full. Full is useful when it can be used as a double bed in a pinch, but no one wants a double bunk bed.

You don't want trundles, unless you are rarely going to be using the trundle and it can move far away from the other bed. But, in that case, I'd think an airbed is a better bet. They can be store more easily, moved more easily, are far cheaper and probably much more comfortable.

Twin and full are 75" while XL twin is 80" long.

The only reason I was thinking full size is so that they could spread out a bit. They are the same length as a twin though. Still figuring it all out. Selling all the current furniture hopefully this weekend! The room will be empty and I can visualize it a lot better! It’s a process! Still leaning towards three XL regular beds now. Will disappoint the kids if I don’t get the bunks but if I do this right it will still look amazing! I don’t have a home in Aspen like the photos on Pinterest with the custom bunks beds lol!

What about an L shaped ( or T shaped) set up?

What a fun project!

I like the L shaped, but we would only have 2 beds (need four - and they won't sleep together). I do like them - especially the ones with stairs where they don't have to use a ladder. I've looked at all of the configurations and none of them worked in this room (not big enough). Unfortunately.

That's my worry (hard to make). I also saw where you buy a nice flat sheet and have a folded blanket at the foot of the bed. I love the zipper comforters but they are expensive and I would have to buy 4! I will check out those Bunk Bed Caps and fitted comforters. Thanks for the info! We have been emptying out the room today and I am making some paper templates to move around the room. I want to make sure I buy the right sized beds and I am a very visual person! I did make a layout of the room with options of full/full and xl twin/xl twin plus one with 3 singles.

Look at how Northern Europeans make beds. Its the most convenient for bunks. Fitted sheet and cotton covered duvet. The duvet gets folded in thirds the short way and then laid on top.

cyprissa - I totally agree with this! I decided against the Beddy's bedding - it's just getting too expensive (I would be spending 1K on just the bedding). I'm going to go for a fitted sheet with a down comforter folded at the end! Still figuring out the beds. Sold the current furniture on Marketplace - they pick it up tomorrow and having an empty room will help me so much as far as visualizing this new layout.

My kids bought an Ikea trundle bed for grandson.We slept on it once. Awful! Bunks are so hard to make & I feel they are dangerous for younger kids.

We use three twins in guest room. It's been great. Older kids declined need for extra long to their regret. Aging bodies don't like changing any beds, but esp. don't like bunk beds. Your grands will forget the bunks as soon as you finish the room.

Really bummed today - made these templates (because now I really do not want bunks) but 3 extra long twins (I know the width is the same as a twin) is too crowded arranged this way. Not enough space between the beds to even get in or make the bed. So I will play around with my computer program and see how I can arrange 3 twin extra long beds in that room. Trundles are not an option, I hate them. Sure, I can put two there and then 1 on the other wall but I don't really like the way it looks and it gives me less room for shelves, etc.