Although it is not a pre-requisite, kitchen islands can help in the ease of movements while working in the kitchen. If you plan to put or include an island in your kitchen and are wondering how big the island should be, here are some tips:

Island sizes vary depending on the size of the kitchen, Tim Carter of : Ask the Builder thinks that an island should be:

No smaller than 2 feet deep by 4 feet long.
3 feet of space from each side of the island.
At the most, 6-feet deep and 10-feet long.
The most important thing is that it is accessible not only for work but also for cleaning. Each top part must be reachable for ease of cleaning.