Is the isle width calculated from counter top edge to counter top edge, cabinet door to cabinet door, or cabinet front to cabinet front?
Are you asking about aisle width (i.e. the space between two cabinet runs or a cabinet and an appliance) or the width of an island (isle)?
The NKBA recommends an aisle width of at least 42" for one cook or 48" for two, measured from counter frontage to tall cabs/appliances. A walkway should be at least 36".
If you're asking about an island you'll have to be more specific.
Excellent question. I just did a search on this the other night. The Kitchen FAQ's provides some good information on this and says to measure from counter to counter (not cabinet to cabinet, or toekick to toekick).
In my current kitchen there was a full 10" difference between the "counter to counter" vs the "toekick to toekick" - which certainly emphasizes how important it is that you and your contractor are using the same method.
Aisle width is always measured between the narrowest obstructions to your passing through a point. If that obstruction is a refrigerator handle or stove handle and your island countertop, you measure the narrowest distance between the two. That's the most restrictive point, and that is the minimum width under discussion. It does no good to have a 36" width from counter to counter, only to have a refrigerator stick out another 12" into that space. You have to measure between that refrigerator counter and the closest adjacent object, and there is no way in heck that 24" between a refrigerator and any adjacent counter will ever satisfy code or work well in a kitchen.
Yes, aisle width. I must have been tired last night. Thank you for the responses. Our plans are drawn for 48" between the cabinets. By the time we account for the counters and range that narrows it down so that we should still have at least 42".