Depends on if I am sewing upstairs or downstairs in my dining room that isn't very big at all. I would say it may be 10 x 10. Lets start with the downstairs.
My computer sits on its own little desk with NO drawers but has a tray that pulls out. So what I do is I push my computer as far back onto the desk as I can, sit my sewing machine in front of it..oh and my computer has this site opened on it "just" in case, I want to read posts. To the right of me is my water cooler that has both hot and cold water. On top of the water bottle itself is a little thingy that holds tea bags and splenda just in case I want some hot tea. On the floor next to that is 2 cases of Ravioli. Hubby says they are for emergencies in case the power goes out we will have something to eat. 2 boxes of Capri Sun juices for the neighbor boy that comes to visit sometimes. Hes only 4 but a sweetheart. Next to that is my upright freezer..its stocked with popsicles, fudgebars, ice cream sandwiches...oh and I think theres food in there that you have to cook. And then next to it is my stackable washer and dryer (I live in an apartment) and behind me is my kitchen table that is maybe 2 feet by 2 feet heck I havent a clue its piled high with stuff at the moment. So you see, if I sew in the dining room, I don't have to get up for ANYTHING but potty breaks!!! Then next to me on the left of my desk I have a spool of blue thread with a needle sticking out of it that I used for hemming up my pants a few days ago, my pill caddy, 2 quilting books, a pair of tweezers for those nasty little hairs that seem to grow out of my chin when my brain goes on overload., a heart coaster with a can of diet pepsi on it minus the pull tab which I save for kidney dialsis for a friend and a snack bag stuffed full of pull tabs that I really need to get to her.To the right of the machine is my best friend Fred (yes I named my seam ripper Fred) my little hotpink mini scissors, a small 3 drawer plastic container that is full of 1 1/2 inch squares for the swap that I joined. And a plastic little tote that has all my thread and bobbins and pin cushion and all the other stuff that I need to sew with. On the pull out tray on my desk is my scissors...All I have to do is reach down and grab them and put them back when I am done.
Upstairs...I have a table that is 36 inches tall nice for standing and cutting but not for sitting and sewing because I am so short, I can't reach the foot pedal. But it is like 60 x60 i think its HUGE. Thats where I cut my fabric, I have a little table top cutting board/ironing board that I use to iron but NEVER to cut...the lines are not straight at all on that thing. There is 2 bookcases full of 'JUNK' some for sewing but mostly just a "catch all". And thats about it.