Agree, I would go with a small rectangular or even a small square. It's just prep, so it doesn't have to be large at all. There are lots of round island sinks but to me, it does remind me of a bathroom sink. Which, I'd rather not be reminded of in a kitchen. Search Houzz photos for island prep sink and you'll see both shapes but I definitely prefer square or small rectangle.

A small sink is pretty useless for any prep work. Get a medium size sink that'll function for prep work.

Frankly, if the kitchen is relatively small, I think a "prep" sink is pretentious. If it's a large kitchen and there is frequently two people preparing meals together it can make sense. But a prep sink for the sake of a "prep sink" because it's a great kitchen "feature" and it's strickly a "design feature" skip it. I'd prefer an island to stand alone without disruption of a sink for a more zen look.

Don't over power your island as you have the main sink to do the big preps.

Ken

Plus is this an island right now or being built for the kitchen. Plumbing is an issue here if an old island with nothing. New construction should have plumbing installed for it. It was not mentioned.

Ken

I'm not sure if you should go round or rectangle... I personally like asymmetric things... But we are putting a medium sized sink in our island (already has plumbing there) because I found that one of the functions I wanted to keep in my island sink was the ability to place my large colander in the prep sink to drain off pasta and other items without worrying whether the main sink was clear of dishes or not. So I think the size you have chosen is spot on... Our island is also going to be 4'x7' but my hubby did choose an undermount rectangular sink. (I originally had a regular top mount sink there, I will have more island surface space with an undermount sink of roughly the same interior size.)

You definitely need to do a rectangular sink not round!

Thank you all for your comments and suggestions. Ours is a large kitchen, with the main sink being quite far away from the refrigerator, the prep sink closer to the refrigerator is more of a necessity than a design feature. This is a new construction and the plumbing has been installed.
I am convinced that a square or rectangular sink will look way better than a round bowl after seeing a lot of pictures and knowing what all of you think. The question now is whether to do a rectangular or a square sink? Will rectangular sink on a rectangular island look good?

Get a rectangular 33" sink.

Our main sink is 32'' I'd prefer my prep sink to be smaller than that.

How small? Can you chop veggies, drain big pot of pasta, fill big pot of pasta, rinse a cutting board or any other such prep tasks in a small sink?

I think the small rectangular sink large enough for a pot and your large colander. I'm wondering that if this area will be prep and chopping veggies, etc, should there be a garbage disposal there too?

Can you post your layout please? That will help determine proper size for sink. A prep sink should be able to handle all major prep and have a disposal. Rectangular would be the correct shape. Check out the Kohler stages 33" or Kohler Prolific.

A island sink is small this one here the island is only 4 feet wide. This should only be veggie prep, not a huge noodle pot. You do that in your main sink!! Go with a 18 to 20 inch size and it would look normal to your island and satisfy your needs.

Ken

7 ft x 4 ft is a good size island. Again, layout matters to determine size. Which way is sink facing? A 33" wide sink is only 24" deep. 48" width is more than adequate

If you go with a 33" size you now have maybe 6 inches on each side of it. You need a second large sink in kitchen?? That 33 inch one would not be wise.

Ken

I will need this sink only to wash veggies and fill a small pot. Attaching layout of the kitchen.

Sunaina, Go with a small rectangular sink for this as you just explained! Do not do a large one as it will not go with the kitchen and look weird. 18 to 20 inch is perfect for your needs and others that in future buyers.

Ken

How many cooks in kitchen? What size is your family? Do you entertain a lot? What's the aisle dimension between cooktop to island? Prep sink is in a good spot layout wise. Make sure you have adequate landing space on both sides of the sink (don't stick it in corner). I would highly suggest a rectangular shape. If 33" is too big for you, consider a 25" wide sink

The sink is going along the length of island, not width. So 7 ft is adequate to accommodate a decent size sink.

Is that the actual layout shown? If so, it will really tick you off if you cannot pass the refrigerator if the door is open and if you can't pass the sink if someone is standing there. I would pull out the island and slide left to accommodate two people to walk by.

Thank y'all for the comments and suggestions. I think I have enough inputs to come to a decision. Will go with a rectangular prep sink.

You need 48" aisles for two people to adequately work in kitchen. Bare min should be 42". u might want to swap the ovens and fridge if the fridge is behind the island.