I'd still like to point out that a tile, to me, is one metre square. If in a narrow passageway one person has to drop to the ground to let the other person past, it's certainly no wider than that.
My estimations are 1 metre by 1 metre by 3 metres or 1 yd by 1 yd by 10 ft, with 1 metre/1 yard's thickness being the floor of the level above and/or the supports on the ceiling as applicable. This makes perfect sense for everything except very large creatures or for how much horizontal room someone takes up when they drop prone.
Dungeons at this scale would be rather cramped by modern standards (modern homes' high ceilings are a symbol of the luxury that common people can now afford), but probably considered quite cozy in a fantasy world, especially for dwarves and kobolds.
Essentially, my definition holds true for at least 80%-90% of the time -- any given creature in any given tile -- which is well beyond standard deviation. =)
The rare cases where someone drops prone (which can also represent pressing yourself flat against a wall) are usually limited to a single creature who has dropped prone. Also, the cases where huge creatures present themselves are too infrequent to require any special handling.
So saith JT. ;-)
That doesn't help you much, though. World record for running broad jump is 8.9 metres. Most people are lucky to do 5 metres of running jump distance, and should probably shoot for 4 metres. Even that's pretty up there (imagine jumping over two adult men lying head to toe).
[ October 04, 2007: Message edited by: JT ]