How big should a kitchen island be?

Ask how big a kitchen island should be and the usual answer is a number of feet. The better answer is a number of inches, and it is not the island's. It is the walkway around it. The island is whatever space is left after the people in the room have been given room to move.

That turns the question around, and it makes the measuring simple. Our guide to planning a kitchen island covers the whole decision, from what the island is for to the lighting over it. This one is only about size, and about doing the sum with a tape measure before anyone draws a cabinet.

1. Measure the empty room, not the drawing

Measure the clear space where the island would sit, from the face of the counter or the tall cabinets on one side to the face of the ones on the other. Do it in both directions. Use what is there now or what the new plan puts there, but use the finished face of the cabinets, because that is where your feet stop.

Write down two numbers: the clear width and the clear length. Everything else is subtraction.

2. Pick the aisle that matches how the kitchen is used

The National Kitchen and Bath Association's kitchen planning guidelines give three numbers for the space around an island. A work aisle, where someone is cooking, should be at least 42 inches for one cook and at least 48 inches when more than one person works there. A walkway, where people only pass through, should be at least 36 inches.

Choose honestly. If one person cooks and the family only crosses the room, 42 inches may be enough. If two people cook together, or the kids do homework at the island while dinner is made, use 48. The bigger number costs you island, and it is the cheaper mistake.

3. Do the sum

Take the clear width, subtract an aisle for each side, and the remainder is the deepest island that fits. Here is an example with made up numbers, so you can see the shape of it. Say the clear space between two runs of cabinets is 120 inches.

• With a 48 inch aisle on each side: 120 minus 96 leaves 24 inches of island.
• With a 42 inch aisle on each side: 120 minus 84 leaves 36 inches of island.

Six inches on each aisle moved the island by a foot. That is how sensitive it is, and why a drawing that looks right can still be wrong in the room. Do the same sum along the length of the room to find how long the island can be.

4. If people sit, add the space behind the stools

Seating changes the sum, because the side with stools needs room for the stools and for anyone walking behind them. The same NKBA guidelines give the clearance behind a seated diner: 32 inches from the counter edge to a wall if nobody passes behind, at least 36 inches if someone has to edge past, and at least 44 inches if someone needs to walk past.

Plan about 24 inches of counter width for each seat. The knee space under the overhang depends on the counter height: 18 inches deep at table height, 15 inches at standard counter height and 12 inches at bar height.

So the seating side usually asks for more than the working side does. Count it as its own aisle in the sum above, and the island gets shallower or the room has to give a little.

5. Walk it before you build it

Numbers on paper are not the same as feet on a floor. Mark the island's footprint on the floor with tape, or lay out flattened cartons, and then walk the trips you make every day: fridge to sink, sink to range, range to the table. Do it once with the dishwasher door down and a drawer pulled open, because that is when a walkway is actually used.

If a second person would cook with you, have them stand in the room while you do it. An aisle that works for one body in the room can fail with two.

6. Check the top before you check the cabinets

An island top is usually the biggest single piece of stone in the house, and slabs come in fixed sizes. Cambria, for example, publishes its Jumbo slab at 132 by 65.5 inches nominal. If the island you worked out is longer or deeper than the slab you like, the top needs a seam or a different material. That is far easier to learn at this point than after the cabinets are ordered. Our countertop comparison walks through the materials.

7. If the sum comes out too small

Sometimes the room does not have the width. A peninsula, an island attached to the run at one end, gives you most of the same counter and seating with one less aisle to find room for. Islands are also the piece most likely to be a size nobody stocks, which is where custom cabinetry usually earns its money, as we explain in our guide to choosing kitchen cabinets.

Bring the numbers, we will draw it

Our Littleton showroom is where you can stand the cabinet lines and the slab samples side by side. Bring the clear width and length from step 1, and which aisle you chose in step 2. We will take the walkways off both sides and draw what is left in 3D, so you see the island and the space around it before you commit. See our kitchen remodeling page for what a full project includes.

You do not have to hand us the whole kitchen. Buy the cabinets and the top and install them yourself, bring your own contractor, or let us handle the job from the first sketch to the last outlet cover. We design and install across the southwest Denver metro.

Related: How to plan a kitchen islandHow to choose kitchen cabinetsKitchen remodeling