A bar overhang is typically 10"-12" 12" is more comfortable for a stool with a person sitting at the bar. You really need 36"-42" between a table & wall or other obstruction for people to be seated & have room to walk behind the pulled out chair. If her are is that small now, then I wouldn't do the overhang. What does she want an overhang for anyway ? It's either an overhang or a table. If she has the overhang- why does she need a table ? Maybe she could do the overhang, remove the table & add some storage cabinets under that 1/2 wall to the family room..... Does she have a dining room ?

You need at least five feet of clear floor space between a table and a seating counter just for the chairs and stools. This assumes that people won't be sitting on both at once, and that there's no walking passage, though there's enough room for people to sidle by.

Six feet is a comfortable distance. Eight feet leaves room for people to walk easily.

You can shave a little off these measures--a very little--if all the chairs and stools have round, pedestal bases rather than legs. Also, if the stools are the narrow, saddle shaped variety, if they have a similarly narrow leg-base.

Best way to convince her is to bring in a stool, or even a chair if she can visualize at all, have the kids all loll around comfortably in the chairs, and ask her to put the stool where people can get by.

There are convertible stools, where you can change them from chair height to counter height, which might work in the space as is, but not if an overhang is being added where it isn't already, rather than the cabinet being reduced.

Granite-girl offers an interesting alternative way to use the space, which might work if what your sister really wants is a bar to serve the children breakfast at. The problem is they turn into teenagers awfully fast and a kitchen table can be really useful for those difficult discussions--besides providing room for all those teenage legs.

Thank you, this is exactly the information I need. She does have a dining room, but it's rather formal and it's carpeted...not so great with 2 kids. The point is that there is barely enough room for the table in this dining nook, never mind adding a breakfast bar to the area. There is less than 36" on both sides of the table to the wall or the counter-top right now. I just think she can't visualize how tight this will be. She's got an obsession with having the counter bar after watching all those home shows. Also, can you tell me if you were sitting at the stools at a countertop bar, how much space would you allow for how far from the bar the stools would be?
Thanks for your advice, much appreciated.

A lot depends on the stool, the person and the overhang.

Rule of thumb for dining chairs and counter stools is that the chair itself takes two square feet (un-pushed-in) of planning space, and the chair with person takes three square feet of planning space. People sitting closely alongside each other at a straight table side or counter take a minimum of 2 linear feet of surface. This is banquet style seating where a good sized person has to push his chair back to be able to get up.

This access standard from a building association might help you.

BTW, the above standards are additive. That is, 36" to edge past stools plus 36" to edge past chairs, is 72" (6') to edge between the both of them. 5' is for squeeze past. And because of all of the chair legs, etc., on both sides, the 8' for walk past is actually a bit wider than double the minimum recommendation.

Most of this has been covered by others above, but to clarify/summarize....

Counter overhangs....

If the planned counter is counter-height (36" high), then the recommended overhang is 15"

If the planned counter is bar-height (42" high), the recommended overhang is 12"

If the planned counter is table-height (30" high), the recommended overhang is 18".

Skimping on counter overhang, btw, will not reduce the needed space b/c people will take up the same amount of room behind the counter regardless of whether you follow the recommendations. If you skimp, the people seated at the counter won't be able to sit as close to the counter itself, but they'll still take up that room behind the counter... People will be less comfortable at the shallower overhang.

Linear seating spacing....Regardless of counter height, the recommended space per seat is 24". So, a counter that's 48" long will accommodate 2 people/seats.

Aisle....If she will have the counter seating on the table side, a bare minimum of 54" is needed b/w them...but you probably will not be able to have someone sitting at the table & counter at the same time and still be able to have someone walk (or squeeze) by.