24" front-to-back. If you don't want to spend the money for one that depth, go no shallower than 22".

the wall cabs are 12" wont I hit my head? while cooking over range?

Our hood is 30" off the cooking surface and 24"D. We do not bump our heads and we're a tall family (5'10" to 6'7"). The only person who has hit their head is my DH (6'5")....and that was from the inside, not the outside! He had stuck his head up into the hood and when he backed out, he hit the back of his head on the inside of the hood!

Buehl: I am curious so I am going to ask...Since 36+30= 66 inches and 5’10”=70 inches, how do you cook if a hood is 24 inches deep without feeling like the hood is in your face or bending under the hood over the stove/cooktop? I discounted a Ventahood because the recommended height was only 30” off the cooking surface so I am really curious about the logistics with your arrangement?

Simply put, you stand in front of a stove when cooking. Plus the range is more than 24" deep accounting for doors, knobs, handles, etc (28" ish is pretty common). Most hoods are mounted at 30" and its fine.

You won't hit your head. Your brain figures out where the hood is after one or two uses, and you will never hit your head. People worry about this too much. I'd be more worried about spending $$$ on a hood that doesn't cover the front burners because it's too shallow so can't do its job properly. What a waste of hard-earned dollars, time, and effort.

Also, if the hood is installed too high, you are giving the smoke and grease more opportunity to escape before it can reach the hood. Again, a waste of the cost of the hood, since you've curtailed its effectiveness through no fault of the hood. A hood should be mounted with a 30-36" distance between the bottom of the hood and the cooktop, no higher, or your effluent will be more likely to escape. Shorter than 30" distance, and it gives a cramped feeling and appearance.

The OP has posted several times about bumping out his/her range. In that case, the hood will need to be deeper, again to cover the front burners. You could also bump out the hood itself by the same distance you've bumped out the range.

I decided not to bump so the range is at standard depth as posted above.