The size of your kitchen island depends on the footprint of your kitchen. Above all else, your island needs to fit comfortably in your space. You'll need 36 inches of clearance around each side of the island to open your appliance doors and allow room to move around. An island width of about 42 inches gives you room for cabinets on the working side of the island and seating on the other side. The length of the island depends on your kitchen needs.
There's no rule that says your kitchen island needs seating, but most homeowners enjoy having a designated place for meals or a spot to sit and talk while cooking. If you plan to integrate seating into your island, it helps to know the kind of kitchen chairs or barstools you plan to use. Taller barstools will require you elevate the counter height on the seating side of your island. If you prefer the look of one surface, choose lower seats. Here are some other considerations.
A long kitchen island can be perfect for dividing space in an open floor plan. It also works as a buffet when entertaining. Set out a feast on the kitchen island, and let guests fill their plates family-style.
A large kitchen island gives you more opportunities to personalize your kitchen. If you want the cooktop in the island, be sure to consider ventilation with a hood. You can plan a portion of the island for preparation or cleanup tasks, too -- either with a small prep sink or with your primary sink and dishwasher. If your kitchen is large, consider adding an undercounter refrigerator or wine cooler. A big island might provide opportunities for display with shelves for cookbooks, serving platters, or pretty dish storage. Choose baskets and trays to keep these open spaces organized.
Finally, when installing a large kitchen island, think about lighting. A smaller island can usually be illuminated with one pendant, but large kitchen islands require two or more pendants to provide adequate task lighting.