I know that Kohler makes a smaller oval sink called the Caxton (15 by 12), I too have this issue and hope people are able to post pics!

You might gain some room by setting the faucet off to the side slightly instead of between the sink and the back wall. Haven't done it yet, but that's what I'm planning on doing with my 18" deep (at deepest point) antique washstand in my PR. Using a dropin sink. The edge of the countertop isn't the issue - it's the interior depth of the cabinet front to back. Sink installation instructions should say how deep the cabinet has to be, faucet directions should tell you how much clearance needed and the spout reach. Cabinet specs will tell you interior depth (18" is exterior). Undermount sinks should gain you a little space.

In our powder room we have a 18" deep vanity which is a repurposed dresser. We used the smallest size Kohler Caxton undermount sink and a single handle faucet mounted at about 2:00 (instead in the middle of the back of the sink). We have a soap dish at 10:00, and they visually balance each other nicely. It worked out fine.

astridh & salbwil - sounds very nice could you please post a photo of your sinks/faucets. Thank you

missleah,
If you check the gallery on this forum, my "finished bath and laundry/bath" is listed under a search for my forum name. The picture isn't very good, but you will be able to see that the faucets fit fine on the vanity.
salbwil

We're about to install an 18' vanity with 19' top. I found the Stylo series from Briggs Industries on Overstock.com and through special order at Lowes (much better deal at Overstock). Several of the semi-recessed or vessel sinks fit a smaller depth vanity. We're using the Cuadroato, a rounded square 14' sink.

Here is a link that might be useful: Briggs Industries sinks for smaller counters

Consider a wall mount faucet in a small bath situation. Makes for easier cleaning too. It's just more expensive up front, and the plumbing costs more because the plumber will have to be so precise. But it's a great look for both modern and traditional styles and solves many a space issue.

Wall-mount is the way to go. Saves counter space..

yes but at least 30% more expensive installation and fewer faucets to choose from...

You can also consider a semi-recessed sink that protrudes a bit from the counter. Mine is made to be accessed by a wheelchair, so comes out further than a lot of them do.

You can find lots of semi-recessed sinks from European manufacturers like Duravit and Nameeks. Mine is from Sbordoni and my counter is 16” deep. But you don’t even need to do that. There are hundreds of 18” deep vanities out there these days. Many are “console“ style like this one:

Modern Ceramic Console Sink With Counter Space and Chrome Base, One Hole · More Info

But there are plenty of floating vanities and regular vanities available that are only 18” deep. SignatureHardware.com has a bunch. Or go to the for sale part of Houzz, or to QualityBath.com, Build.com, or any bathroom site and adjust the search parameters to 18” deep and the width you want to see what is available. You absolutely do not need a wall-mounted faucet.

As for how much space you need for clearance around the sink and faucet, it all depends on who is doing the countertop. If you are having a local stone company do the top, ask their rules. I tried to work with a couple of the companies near me befor buying my sink and just gave up. Sales people often have set numbers for where it “should“ go and cannot answer questions for non-standard sizes. I tried writing very specific questions to the actual stone cutters to help me figure out which sink to buy and got nowhere. No one would answer at the place that had my quartz. That is how I ended up with a walnut counter. My carpenter is a genius and I knew he could cut those angles for me. You may find it easiest to buy a vanity with the top included. I did not have that option because I needed to wheel a chair underneath my vanity.

I solved the issue by searching bar sinks and RV sinks instead of bathroom sinks. Smaller options came up in searches. I found a lot to choose from. I settled on a undermount porcelain oval sink 10" x 12" x 6-1/4" deep.