I just got a large migration in my already medium sized beds. I think I have enough beds for everyone (I have assigned rooms), but Im not sure. How can I get a count of all the beds in my fortress (built and in storage)?
You can use the stocks screen. From the 'z' menu (status), use the arrow keys to select the stocks option. Hit enter. Move down the list until you find the category 'beds'. There should be two numbers, one in grey and one in red. The grey one is the number of un-built beds you have, the red one is the number of built beds you have.
In order to use this method you have to have a bookkeeper who has done enough work to count your beds. If the column shows a number with a question mark in it then you need to have your bookkeeper do more work.
If you don't have a bookkeeper, or don't have one who's been trained up enough to have perfect accuracy, there are some other ways to find the information you're looking for.
First, when you do place a bed, make sure it's set up as a bedroom:
query to select the bed,
resize to the size of the room you want, then
Enter to set it. If you then leave it alone, dwarves without bedrooms will eventually claim the room, and they'll have a bed.
Your new migration wave will eventually claim any unclaimed bedrooms, and have their own beds. You can check to see who has a bedroom already claimed by going to a bedroom you've designated, but is still unclaimed, then
query the bed for the bedroom, and
assign the bed. The green dwarves are the ones who haven't yet claimed a bed. You can scroll through this list to see how many dwarves don't yet have bedrooms.
Finally, you can see how many beds you've have created, but haven't yet built by using
bed. The screen will show "Placement", if there are beds to be built, or "Needs bed" if you have none left un-built. If you have some to place, arrow to your location you want the bed,
Enter, and then you'll see a list of the beds to choose from. They'll be listed as something like "acacia bed, dist 26, 0/8", suggesting there's an Acacia bed 26 steps away, and you have 8 of them un-allocated somewhere.