Ideally allow at least 3 feet for each chair (2' chair depth + 1' to get in and out). So if you have a 12' space, 6' might be taken up by chairs. That means you can fit a 72" round but wouldn't have a lot of extra space. The leaf would make it really tight.

I'm all for extra space, but I fell in love with a round table, so I will deal. I have an 8x8 space plus walk room on one side, and I picked out a 48" round table. I have no extra room on some sides but the roundness helps.

There are a lot of options. I would go into a showroom and ask the sales associate for help. There are convertible tables, thin pedestals, variable tabletops, exterior and interior legs, 3 legged tables in addition to leafs.

Sorry that was probably not much help. I went into a crate and barrel showroom and asked for help and I was able to figure out what I wanted through the process of elimination. They have enough different configurations that you can get an idea of what will and will not work in your space. I would optimize floor space for your family and only add the extra tabletop space when you absolutely have to.

The chairs make a big difference in how much space you have around the table when not in use. You can choose uncomfortable chairs that fit tightly against the table (if the table allows) or comfy upholstered chairs that take up more space when pushed in as much as possible. If you go rectangular, you have the option of benches. They have upholstered benches too.

Every inch matters. If you can trim a few inches off the chairs or table edges or scooch the chair under the table a bit more, you may be able to come up with another 6-8" around the table.

This one says it will fit 6-8, but I wonder if you could get more kids around it if you use benches. (It's not the most attractive IMO.) Table goes from 34x57 to 57x68.

I have a 12x12 dining room. We have a sideboard and a 48" round table (generally seat 4 there but have fit 6 tightly). It was a thread on here that convinced me a rectangular table is better suited to my small square dining room and will accommodate more people. I love round tables but I'll have to sacrifice to fit more people!

I have a Trestle table and I like it because you can easily get two people on each end because there aren't table legs that get in the way. I love the way settees look at the end of Trestle tables.

Thanks for your input. I'm realizing that the bay window makes the room appear much larger than what it really is. Also, the room is currently empty so it's hard to visualize what size table will fit nicely.

About the chairs: I am debating between two different chair models. One is 18''1/2 wide by 24"1/2 deep and the other one is 21'' wide and also 24''1/2 deep. I feel like the wider chairs would be more comfortable but less appropriate for a round table. Is 18''1/2 wide too narrow for a dining chair or would you think it is equally confortable as a wider chair?

My chairs are 16.5" wide. The width is fine. The parsons chairs I picked are 18" wide IIRC. They are 23" deep which provides a few more inches around the table. I will need every inch.