19 inches. That's the gap between my sofa and coffee table after I wedged in a set of nesting stools I thought would slide under cleanly. They didn't. The legs caught on the table's lower shelf, and I had to yank them out sideways, scraping the finish. I returned them the next week. That was my second failed attempt at the whole "chairs under the coffee table" idea.
The first failure was a pair of upholstered cubes. They fit under the table height-wise—22 inches of clearance under the tabletop—but they were 18 inches deep. The table was only 16 inches deep from the front edge to the back support bar. So they stuck out two inches, which meant anyone walking past clipped them with their shins. My living room isn't a hallway, but it might as well be with the way we move through it.
I learned the hard way that "chairs underneath" isn't a style, it's a geometry problem. Here's what I measured before my third attempt, and what I'd tell anyone else doing the same.
The space you're actually dealing with
First, measure the floor area in front of your sofa, not the sofa itself. In my case, the sofa is 90 inches wide, and the wall opposite is 11 feet away. That leaves about 5 feet between the sofa edge and the TV stand. Sound like enough? It wasn't for a table with chairs.
I drew a rectangle on the floor with painter's tape—the footprint of the table plus the chairs pulled out. For chairs to be usable, you need at least 24 inches of pull-out room in front of the sofa. That means the table can't sit closer than 18 inches to the sofa, or the chairs will hit it when you slide them out. And if the table is deeper than 20 inches, you're squeezing the walkway behind it to nothing.
My eventual table is 40 inches long, 18 inches deep, and 16 inches high. The stools I kept are 15 inches tall and 11.5 inches deep. They tuck fully under with about an inch to spare. The walkway to the TV remains 36 inches—tight but passable.
Chair dimensions, not catalog pictures
Nobody lists the depth of a stool under the table in the product photos. They show it from a 45-degree angle with a throw blanket draped over it. Ignore that. Get the actual dimensions.
I looked for stools that were at least 2 inches shorter than the table's clearance (measured from the floor to the underside of the table's support beam, not the tabletop). My table has a lower shelf, so the clearance is 13 inches from the floor to the shelf's underside. My stools are 15 inches tall—they don't fit under the shelf. They fit under the tabletop only because the table's legs are at the corners, and the center is open. I made sure the stools were narrower than the gap between the legs. That's another measurement people skip.
Also, consider the seat material. My first cubes were fabric, and they picked up dust bunnies like they were on a mission. The new stools have a wood seat with a low-profile metal frame. Easier to wipe, and they don't look like they belong in a preschool.
What you actually need chairs for
Be honest: will you pull those chairs out for guests, or are they just decoration? If it's the latter, you can get away with almost any stool that fits under. But if you're like me and you host game nights where people need a place to sit without dragging in dining chairs, test the pull-out motion first.
I set up my new stools in the store, pulled them out, sat on them, and pushed them back. The key was that the stools slid out without catching on the table's support bar. That meant the stool depth had to be less than the distance from the front edge of the table to the back leg. On my table, that's 14 inches. My stools are 11.5 inches deep, so they clear with room. If the stool depth is even close to the table's depth, you'll have to tilt them to get them out, which gets old fast.
One more thing: if you have kids or pets, the chairs under the table become a collision hazard. My cat loves to hide under there, and I've almost shut her in twice. Now I keep the stools pulled slightly out so she has her own gap, but that means the walkway shrinks by another two inches. Worth it, but know it before you buy.
The one measurement that decides the buy
The depth of the chairs versus the depth of the table's under-shelf space. Not the height, not the style, not the color. If the chairs don't slide all the way in without sticking out, you'll hate them within a week. I have a 14-inch clearance front-to-back under my table, and my stools are 11.5 inches deep. That inch and a half of margin is the difference between a functional setup and a constant annoyance.
Measure your table, measure your chairs, and respect that gap. If you can't find chairs that fit with at least an inch to spare, move on. There's always another table.
For more on sizing furniture to your actual room, don't miss the 30 Round Coffee Table guide or I bought a dining table with padded bench. And if you're measuring for chairs that need to fit under anything, the comfortable kitchen chairs article has the same math.