Depends on what brand and model you choose, but if you choose fully integrated appliances, then they are the same 24 3/4" (excluding handles) that traditional cabinetry is. (Cabinet boxes= 24" + 3/4" doors.) But in a kitchen that is expensive enough to do built ins, custom cabinet depths are often used because some integrated appliances (some DW's and warming drawers for instance) aren't fully integrated without a little bit of extra depth available.

So the answer is, "it depends".

As Hollysprings said, depth depends on the manufacturer and model. Refrigerators, for example, range from approximately 24" deep (limited to specific "counter depth" models) to perhaps 28" or so (the more common models). Best bet is to get the spec sheet for the specific refrigerator and use those exact dimensions.

Ovens generally are designed to fit into a large cabinet and tend to be about 23"-24" deep. Again, getting and using the spec sheet for the specific oven is best.

Not sure about ovens, but most built-in fridges tend to be much more costly than regular fridges. Our architect is recessing our fridge, so it looks like a counter-depth built in, but isn't.

If you are able, select a fridge you really like, then have the architect figure a way to recess it :)

Thanks for the replies. I was looking at some of the specs and as HS and VC stated, it depends on the installation type and whether they will be flush (integrated) or built in.

This comment may not be directly pertinent, but we discovered too late in our build that our counter depth fridge at 24" actually sticks out to 25" due to the required 1" clearance behind the appliance for the water line, etc. thus our fridge still sticks out of the cabinetry opening built for it, which is a shame. Our counters are 25" so if we had just extended the wood panel out to match, we'd be in good shape.

Not sure if true built-ins have this same design consideration, but thought I would share our experience.