Room Sizes

A little idea as I get back into things -- In some adventure products you get boxed-text room descriptions like, "The double doors open into a courtyard that is 80 feet deep and 90 feet wide. Once well cared for, the dirt floor is now choked with weeds. In the center of the yard sits a large pool, etc., etc." [D&D Module B7 Rahasia, Tracy & Laura Hickman, area #2]

There's a debate to be had about whether giving the room dimensions (80×90 feet) at this point is justified. Cognitively, you'd think that (a) the PC's attention would be first attracted to the stuff in front of them (especially any hostile monsters!) before dimensional details, and also (b) to get exact footage you'd probably have to get in, explore, and pace it off. The counter-argument, I suppose, might be that letting the players draw the area on the party map allows them to mentally situate themselves there. Sometimes I go back-and-forth about whether the dimensions should be the first thing described, or the last.

Here's a synthesis: Give the players some notion of room size first, quickly, by just using the terms "small, medium, or large". Only give exact dimensions after a fight has been resolved, and exploration/ searching/ pacing/ mapping is possible. Of course, this requires some kind of consistency in your "size" descriptions, such that you're playing fair with the players. Here goes after a bit of research:
  • Small -- Up to 200 square feet (10×10 or 10×20). Small living quarters or chapel.
  • Medium -- Up to 2,000 square feet (from 20×20, 30' diameter around, to 30×60 or 40×50, etc.). Tower central room, guard hall, castle kitchen, big living quarters.
  • Large -- Up to 20,000 square feet (from 50×50, up to 50×100, max 100×200). Keep great hall, largest DMG Appendix A room/ chamber/ cave size.
  • Huge -- Up to 200,000 square feet (from 100×200, 150×350m, max 400×500). Major cathedral, largest DMG Appendix A cavern size.


  1. I've always been interested in how dungeon maps in general are drawn with the DM in mind as audience.

    I think most players have a very simplified, flow chart like mental map of a dungeon's twists and turns. I think translating dimensions into verbal descriptions as you suggest would be helpful players.

    As a player I want to know whether this room is big, small, bigger than the last room, etc. 35x45, etc. doesn't do much for me personally. Thanks.

  2. I go with guesstimate dimensions, which are sometimes accurate and sometimes higher or lower (sometimes radically so) depending largely on the whim of my descriptive muse. If they want measurements which are guaranteed to be accurate, they need to spend the time measuring it.

    I'd also be concerned that using any kind of systematized and simplified system (small/medium/large/huge) will tend to turn the world into vanilla: There's a danger that everything becomes too "samey".

    It also adds a bit of difficulty in communicating room proportions ("square", "longer than it is wide", and the like will become useful, naturally).

    I do feel it's important to give the players as much information on as many verbal channels as possible: The characters experiencing immediately a vibrant world using all of their senses. We're trying to communicate all of that detail using little more than the spoken word.

    For example, we worry about the players metagaming if, for example, we tell them exactly how difficult it will be in mechanical terms to jump across a particular crevasse. But I find that this mechanical certainty is a closer analog to the character's judgment in actually looking at the crevasse than a player judgment in parsing a vague and potentially misunderstood verbal description.

    @Telecanter: After a long period of not featuring player mapping, my current groups have all migrated back into using them. The first time their "rough estimate" map stops making sense to them is the point where every single player I've ever seen suddenly becomes very interested in precise measurements.

  3. When I initially describe a room or passage, I usually do so in terms of how far the party's source of illumination reaches. So a corridor that's 30' long reaches its end just at the edge of their torchlight. A room that's 60'x60' is larger than their torches can reach on first entering; they have to move about midway into the room to even get a glimpse of the far wall. And so forth.

    If they take the time to pace out the room, search it thoroughly, etc., I will give the dimensions. This takes the btb 1 turn per 10' square space.

  4. The 80x90 could be a rough size. If paced out carefully, it might turn out to be 78x95.

    The difference could be important in terms of mapping and finding secret doors.

    I think when people are in rooms of familiar scale (a bedroom, a conference room, etc), they can probably estimate to within 10'. Of course, lighting matters, and can distort perceived distances.

    For larger spaces (the food court of a mall) I think they'll probably be much less accurate.

  5. I think it is reasonable for the characters to know a somewhat accurate size for rooms. There would be various things to tip them off such as the previously mentioned visibility by torch, how the floor is tiled or they happen to have a 10ft pole with them for comparison. In a fight I would be vaguer but unless its a natural cave or something most intelligent creatures make rooms that fit them and humans happen to have this thing for rooms in increments of 10x10x10.

  6. Couple additional thoughts as this post has been hanging around with me all day:

    (1) Although in reality a person's attention is likely to be riveted to the most important features (like bad guys pointing guns at you); I think it's generally better from a pacing standpoint to build up to that exciting moment. Establish your scene and then add the active contents demanding response (so that the players can give that response immediately instead of waiting for the rest of the description).

    Exceptions to this rule almost certainly exist.

    (2) My own thoughts are currently being formed by two campaigns I DM: In my OD&D game, I don't use a battlemap and my distances are all imprecise. In my 3E game, I use the "battlemap every room" method, which means that measurements are always precise.

    In terms of gameplay, the effect is minimal. One would think that the imprecise distances would increase map inaccuracy, but other mapping errors by the players seem to compensate for the difference. (This might be different in a game with a more meticulous mapper.)

    So the only real knock-on effect is one of versimilitude: If they want a precise map, then their characters are forced to take the time actually required to get that precise map.

    In practical terms, therefore, the difference only becomes important when time is a factor. Which 9 times out of 10 means, "Is there a risk of a wandering monster encounter?"

    Without wandering monsters or similar elements which cause time to matter, imprecise measurements are almost wholly irrelevant.

  7. Good thoughts here. KenHR's comment on lighting source is great, that's one that's easy for me to forget -- quite likely the most important distinction is a yes/no "can you see the far wall/ceiling or not" qualification.

    I think building up descriptively to the hostilities kind of rubs me the wrong way. If I've got players opening a door with something about to attack them, I think cognitively that's got to be mentioned within the first sentence of feedback (e.g., "A small room with bookshelves, an angry wizard looks up at you, roll for initiative!".)

    As PCs move into the room, even under hostile action, I'd be more liberal about giving them 10-foot approximations of the space they have around them.

  8. Are your measurements for rooms only or also for building them self? Also what about gargantuan and colossal, is this info sourced somewhere?

    1. The idea here was just to measure rooms with PCs on the inside. As noted above, "Huge" encompasses, the largest possible cavern size noted in the 1E AD&D DMG, so I didn't see any need for larger categories.