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Shelf spacing calculator

Equal gaps in any opening.

Open the Shelf Spacing tool

Free. Runs in your browser, no account, and keeps working offline.

What it does

Enter the inside height of the opening, the shelf thickness and how many shelves you want. The calculator spaces them so every gap is the same and gives a mark for each shelf — its bottom edge, center or top, measured from the bottom or the top of the opening.

Choose whether there is a gap above the top shelf and below the bottom one (shelves in a bookcase or closet), or whether the top and bottom shelves sit flush in the opening and only the gaps between them are equal.

Use it for built-ins, closet shelving, cleats on a wall and pantry layouts: anywhere a set of boards needs equal space between them.

Worked example

An 84″ (7′ 0″) tall opening, three 3/4″ shelves, an equal gap above, below and between them.

Equal gap
20 7/16″
On center
21 3/16″
Shelf 1: bottom edge from the floor of the opening
20 7/16″
Shelf 2: bottom edge from the floor of the opening
41 5/8″
Shelf 3: bottom edge from the floor of the opening
62 13/16″
Try it with your numbers

Questions

How do I space shelves evenly?

Subtract the total thickness of the shelves from the opening height, then divide by the number of gaps. With a gap above and below, there is one more gap than shelves.

Do I mark the top or the bottom of the shelf?

Either. The calculator lists each shelf's bottom, center and top, so you can mark whichever edge your cleat, pin or bracket goes under.

What if my shelves aren't 3/4″?

Enter any thickness. Plywood is often a little under its nominal size, so measure the actual board.

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