24" elbow room on counter, and 15" knee space per seat, so 39" x 48" for the seating end. With two 39"+ cabinets, you're looking at a ten foot island. And if using back-to-back 24" deep cabinets, you'll need at least an inch overhang on each side, so 39" x 50". If no other choice, you could fudge a few inches, since the elbow room for each stool on the long sides could slightly overlap the counter space over the island cabinets. (Shoulders are wider than hips and knees.) Can you post a drawing of the layout, with adjacent rooms marked?

[New to Kitchens? Read me first.[(https://www.houzz.com/discussions/new-to-kitchens-read-me-first-dsvw-vd~4306041?n=585)

NKBA guidelines, #9 specifically.

30” per person where the single chairs are plus 15” more to accomorate the two end chairs leg room would be minimum 24+6+15= 45” in total.

The minimum width where the two end chairs are would be 24+24+6+6=60”

why you need this wider than normal length is bc of your two island posts, allowing 6” for each side of each post. Also, you need to increase these measurements if people in your house are above average size. What do you think?

I have seen seating for 3 stools on a 72“ length. You might cut down inches if you do not have those big chairs, stools instead. If your posts are skinnier or the support is running in the middle of the sitting space, you will save on inches again.

now the measurements can be as Mamagoose said.

I was hoping I could get away with no posts, brackets instead. I have since decided on just two stools (not big chairs) at the end of the bar. Thank you all so much for your help.