I'm guessing 27" to 28.5" external width.

You would need to check specifications for each sink as they will state required cabinet size.

I've done a lot of research on this as I am considering a 30" Ikea cabinet (so I can have pull-out trash underneath). It obviously varies by manufacturer and design, but my goal is to get the biggest sink possible, and a few I've found are:

Create Good Sinks (link). I assume the 28" ledge sink would work in a 30" base, but I'm not sure as I couldn't find a statement on the website. Kohler's website has this info, which is why I'm leaning towards them.

Kohler Strive (link). Specs say it is 29" x 18-5/16" x 9-5/16" and will fit a 30" base cabinet - "The increased dimensions of this sink maximize the space in a 30-inch base cabinet" - but also that a 30" cabinet "may require cabinet modifications" (I'm not sure what that means). That last bit makes me nervous.

Kohler Riverby (link). 27" x 22" x 9-5/8", fits a 30" base and comes with accessories including world's tiniest cutting board (like, literally 7x7").

My sink spec said it needed a 33" cabinet, and I put it in a 30" cab. I bought the sink before my custom cabinets were fabricated, so if we needed to add a little width to the sink cabinet we could, but it wasn't necessary.

As buehl indicated, the critical dimensions are the interior of the cabinet and the exterior of the sink.

It's partly dependent on how you install. If you use the provided clips you're limited to a smaller sink, but if you use a harness like a HUSH, you can often use a sink that's advertised as being the same size as the cabinet itself, since the actual outer bowl dimensions are usually less.

Joseph Corlett should be along to elaborate on that, I would think, but if you search for his posts here, you'll find plenty of examples

This is a question for another thread, perhaps, but I wonder how you can get a plumber to use a HUSH if he's not familiar with it? I'm completely convinced of their utility, but I can also see a plumber saying "okay, little lady, thanks for the suggestion," patting me on the head and doing things the way he's always done them.

Yeah, there is definitely that, cs929. Where are you? If you're in FL, you could just call Joe.

If only! I'm outside D.C. This is actually something that freaks me out about the whole renovation that I am planning -- I'm a woman, I'm single, and I'm not a construction expert but I know some things. I don't want to spend all of my time trying to convince some guy that I KNOW what I want. Anyway, let me stop with the thread hijack. Maybe it's worth me starting another thread later on, to see if others have gone through a similar situation.

No worries on the thread hijack. I was wondering if the HUSH system would work. Maybe Joseph will comment.

Thanks for the list AMS I will have a look at those.

You can put a 30" sink in a 30" cabinet, if you strap it.

Awesome, thanks Joseph! By strap you would suggest the HUSH?

Thanks, Joe. I know you've said this before, but I just saved it in case I need to convince my contractor.

I wonder how you can get a plumber to use a HUSH if he's not familiar with it? Put in writing the specifications of the work required during the bid process and have a contract. You are the consumer and are paying for the service you want done, not what the contractor feels like doing. To make yourself more comfortable, print off documentation/specs and have an itemized listing of the required work that you hand to the contractor that you are asking for estimates. If they refuse to perform the work you require, or aren't willing to research a valid process, practice, or product, you don't want to hire them. I've worked with contractors my entire life and they have a difficult time arguing with knowledge and facts.

Great advice, but do I want them to practice on MY sink? Which leads me to the next question: How difficult is it to use a HUSH?

If your contractor can't figure out a HUSH, you need to fire him immediately. This ain't rocket surgery.

Joseph, I have read a number of comments about standard sink bases being able to fit same size sinks with straps. We will have a 42 inch corner sink cabinet. Looking at the Elkay crosstown sinks with offset rear corner drain. Measures 31 1/2" exterior, 28" interior wide. If using the HUSH will this sink fit without scooping into cabinets? Also would like to have only 3 or 4 inches at most counteredge to sink. In otherwords I know we can push the sink back and fit a larger sink but we don't want to. How wide of a sink can we get?

The corner cabinet throws a wrench into the works. You'd have to provide detailed drawings and specifications for me to attempt an answer, but even then that's going to involve pushing the sink back and only you can decide that tradeoff.

Yes, as long as it's a short apron undermount.

Looks like we will be going with a drop in sink. Hw does this change the goal of fitting the largest sized sink in an IKEA 30" sink cabinet?

The sink and cabinet don't care or know if they are undermounted or dropped in. Nothing changes.