All of it.
One room apartment with kitchen and bathroom. 37 square metres.
With that amount of space, I’d think I’d find it difficult not to use all of it.
It’s fine for one person + cat; not surprisingly, I tend not to have people I don’t know extremely well to stay.
We have a 2-story, 4 bedroom, 3 bathroom house. 3000 sqft.
Spaces we use everyday:
Master bedroom and bath
Library (which was the formal living room when we moved in)
Kitchen
Breakfast nook
Family room (really the living room, since the formal living is not used as such)
Downstairs bath
Sun room (which opens off the family room)
Spaces that are used rarely:
The room over the garage – there is an extra TV up there, and my craft supplies, and the treadmill. I’d like to say I go up there every day to use the treadmill, but that would be a lie. There are weeks when I don’t even go up there once.
The kid’s bedrooms. Only used when the kids are home, or when we have guests.
Upstairs bath – again, only used when my son is home, or when we have guests.
Guest room
Formal dining room – we walk through it from the kitchen to the front door, or to the stairs, or to the library. But we only really use it a couple of times a year.
Caveats:
My husband used Nick’s old bedroom (our son) as his office when he is home. He travels for business, but when he is home he uses his office everyday.
We use all of it. The only room I’m not in every day, doing something, is a spare bedroom.
A good friend remarried about two years ago. She has custody of three teenagers and he has two who visit on weekends. They built a house with six bedrooms so each kid could have their own room. Now only one kid lives at home. She says they hate having all that unused space, but they felt they had to do it to blend the family without anyone feeling left out.
I moved just over a month ago, partly because the old place was too big. It was a 3-level, 3-bedroom, 2.2-bath townhouse, and I didn’t use about 1/3 of it. Upstairs I used 2 of the bedrooms (the third was occasionally a guest room, but mostly a storage/ironing room), the middle floor was the kitchen, dining room, and living room (all of which I used regularly), and the basement was the family room and laundry room/storage. I only went to the basement once a week, to do my laundry – the family room was completely empty. There was a half bath down there that only got used if I had guests, and one of the full baths upstairs hardly ever got used because I always used the one off the master bedroom. It was my first townhouse after 9 years of apartment living, and I think I went a little overboard (“space! give me space!”).
So now I’m in a 3-level, 2-bedroom, 1.5-bath townhouse. Doesn’t sound much smaller, right? Well, in this place the middle level consists solely of the kitchen and dining room: the two bedrooms are upstairs, and the basement has the living room and laundry room. The dining room lofts over the living room, and is one of the things about the house that I like. So I still have the same amount of stairs to deal with, but this time I’m living in the entire house. In fact, all of my stuff just fits in this place – and I even gave away/sold a bunch of stuff before the move. 
We hardly use any of our house. We have three porches that I think I’ve sat on once or twice in the past 5 years. Besides the bathroom & basement for laundry, we use probably 3-4 rooms in the house. Most of the rest of the house I only go in to clean. I compulsively throw things away so there’s hardly anything in most of the closets.
It’s a large house, too large for 2 people at the moment and a dog. Four bedrooms, 3 1/2 baths and a yard that’s a full time job. The house has been in my husbands family so he doesn’t want to move, or I’d look for a new smaller house tomorrow. This house has 22 windows not counting the sun porch. I know because I washed them the other day. 
We have a two-bedroom place, with two baths (one a three-piece). The only room we don’t use is the second bedroom, because it’s just being used a giant closet/storeroom. Does that count as ‘using’? We’re actually in a doublewide mobile (and no, never in my life did I dream I would inhabit one of these, but in a hideously expensive housing market–Victoria, BC–that’s what we got. We have a livingroom/dining room combo, kitchen, entry, den, two bedrooms and two baths. The only room that doesn’t get used every single day is the storeroom bedroom.
The two of us live in about 2,200sqft and have 800sqft of basement storage.
We use the bedroom, living room, and kitchen every day. Ancillary spaces are the cats’ bedroom and both of our offices as well as the music room/parlor and formal dining room; the cats’ bedroom is mainly used by the felines, with humans stopping in to perform vital services; the parlor and dining room are used whenever guests come over and the offices are now 'n then usages.
I can say that when we lived in 900sqft in SoCal, we squeezed out every square inch of living space and overflowed even then. I’m not in love with our new state, but at least we can enjoy what for us is a huge house.
Funny story: My parents bought and renovated a 20,000sqft former school. They’re both packrats and the ground-level (5k) has filled up with exercise equip, furniture, tchotchkes, guns, etc. Mom decided to move some of the ex. equip out of the living spaces and was fretting about where it could possibly go until I reminded her that they had 15,000sqft of empty space on the second and third floors.
Two of us live in a 2-bedroom 1930s terraced cottage. I estimate it to be 1200 sq ft. We use everything but the guest room. I’d like a place with a bigger kitchen, a little more storage, and a separate toilet, but apart from that it’s totally adequate. I think we’d rattle around in somewhere much bigger.
Well, of my 114.5 sqaure feet, about 65% of it. It helps when you don’t actually have much stuff to throw on the ground.
I have about 1,000 square feet and I use pretty much all of it.
My dining room only gets used when I’m entertaining - I never eat in there by myself (that would be goofy), and my spare bedroom mostly gets used for the closet. Although this past summer I decided to sleep in there just to mix things up a bit.
Now I’m back in the master.
My house is 1600sf, three bedrooms with 2 people living here. I have 2 three season porches and a basement. Living room rarly used. Dining room rarely used. Side three season porch is never used. We have a guest room thats occasionaly used. Mostly we use out two bedrooms. The stair landing and the kitchen and the laundry room. The basement is to short to be useable for anything besides storage. The front three season porch collects stuff. Every once in a while we clean it so we can hang out there.
I hate all the massive complex houses they keep building. I just don’t understand people buying a 5000 sf house for 3 people. Then they complain about heating costs. Around me McMansions keep being put up. Gigantic houses made as cheaply as possible.
5 bedroom, about 2300 sq ft. We use all of it, except for the kids’ two bedrooms, since they are at college. My older daughter is pretty much gone to grad school, except for XMas visits, the younger reoccupies her room during the summer. One bedroom is my wife’s office, the other has my computer and sf books. We have to family room areas, one for the TV and one for the stereo, and where I do my puzzles.
I could use more wall space for more bookshelves…
We have 4 bedrooms and 3 1/2 baths. We use the master bed and bath, the living room, kitchen, family room (the other TV is in there, so I can watch stuff while Mr. 1341 watches football), and the kitchen. The 1/2 bath is also the laundry room and there is a litter box there, so we use it regularly.
We don't use three of the bedrooms and one of the baths- Mr. 1341 uses one of the "guest" showers most of the time so we don't get in each other's way when we're getting ready for work.There may be a square cubit or so under the fireplace that I’m not using, but given that a) it’s not a very big house (the MLS writeup said 1050 square feet, but it lied), and b) I’m an incurable packrat (“I may need that 1977 Visa statement someday”), I don’t think I could get by with less.
I live in a 4/3 with four other people (and a Guy on the Couch who, sadly, is leaving us for Hollywood tomorrow to start his film production internship). Every square inch of the house is used, even the Harry Potter room under the staircase. I can’t think of any good we could get from adding another room, though.
Now that I think about it, we don’t use the dining room much, unless there’s a D&D campaign going on. Even when my roommate cooks for him and I (two of the other roommates work at Round Table Pizza and only ever eat take-out pizza, and the other one jams the kitchen with her own food and refuses to share), we usually eat in front of his computer or the PS2.
We have almost 1300 square feet - 3BR, 2BA, LR, and EIK. We use our BR every day. Spencer “uses” his room mostly for his stuff and naps. The third BR is my office and the computer room. I’m a Mary Kay consultant, and having this room 100% an office gives us better tax breaks than when we had the spare bed in here. We also have a small front porch, which we used when we smoked, and a large back patio, which we rarely use. Our only issue is that our previous house (a rental) had a basement, so we had room for our random crap. Also the rental’s “garage” would barely fit a Mini Cooper, so we had plenty of space for our lawn stuff. Now, the Christmas decor, lawn care, and camping stuff has to fight for space in the 2-car garage. We haven’t used it since March, but we will have it cleaned out before the first snowfall.
We have about 1600 square feet plus a two-car garage–4 bedrooms, 2.5 baths, dining area, living room, family room–shared between two people (me and the spouse) and five cats. We use pretty much all of it, with the exception of the living room. Neither the living room nor the family room is very large. The family room contains the TV, a large couch, a large chair, and a cat tree, and it’s pretty full. The living room, somewhat bigger, contains a chair, a couch, a never-used fireplace, a large coffee table, and a storage unit thingy.
The problem is, the couch and the chair in the living room are rather unhospitable for sitting–they’re covered with decorative pillows which have to be dealt with (tossed on the floor, whatever) if you want to sit on them, and it always seems too much trouble. I’ve been saying for awhile that we need to get rid of the furniture in that room (even though I’m really quite fond of the couch, aesthetically speaking, and the chair is very comfortable if you make the effort to sit in it). It just bugs me that the largest room in our house is basically useless and is usually nothing more than temporary storage.
Just the idea of having completely extra, unused space in one’s house or apartment gives this New Yorker… well… a tingle of forbidden desire?
Reminds me of this cartoon I saw a long time ago while saving up to buy my first place. Oh, it’s true. It’s very, very true…
I live alone in a small two bedroom of maybe 600 square feet. The small second bedroom is my office but since I got my laptop, it mainly just holds my books and the litter box. So I live in about 475 square feet.
Our family of 4 is in a 2000 sq’ ranch of 4 BR, 2.5 Baths, LR, DR and Family Room.
We have an attached 2 car garage and a full basement which includes my large wood shop, a den, a Pool Table and Train table area and much storage. Our attic has very little storage and low ceilings.
We use every room to the max except the Living room, this ends up being the Piano room, Reference Library and hallway from DR to MBR. The Garage parks both our cars and our Tractor and a workbench. It has overhead storage I minimally use. So my house is about 85% to 90% utilize.
I wish the layout of the house was a little different, I would like more seating in the Family Room and to a smaller LR but a fifth Bedroom to make a separate office and Guest room. My office is well cluttered with 2 computers, the guest bed and completely filled shelves everywhere. Actually my entire house is heavy on clutter, only the Kitchen & Dining Room escape this.
I occasionally think about adding on a new MBR Suite to the back of the house and giving my daughter our room and making her room the Guest room. I doubt I will ever do this.
Jim