Free tool · Cabinet & door sizing

Shelf Spacing Calculator

Enter the opening height, the number of shelves, and the shelf thickness, and get the even gap between them plus the exact height of every shelf.

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A free tool from Fast Kitchen Design. We draft kitchen and bath cabinets in 2020 Flex for a flat $100 per design, delivered by 9 AM.

See how it works

Shelf Spacing Calculator, explained

How do you space shelves evenly?

To space shelves evenly, subtract the total thickness of all the shelves from the opening height, then divide what is left by the number of gaps. With N shelves inside an opening there are N + 1 gaps (one above, one below, and one between each pair), so the even gap is (opening height - N x shelf thickness) / (N + 1).

For example, three 3/4 inch shelves in a 36 inch opening leave 36 - 2.25 = 33.75 inches of space across 4 gaps, so each gap is about 8 7/16 inches. This calculator returns that gap and the exact height of the bottom face of each shelf, measured up from the inside floor of the opening, so you can mark your shelf pins or dados precisely.

How it works

How the Shelf Spacing Calculator works.

Formula Even gap = (opening height - shelves x thickness) / (shelves + 1)
  1. Enter the interior opening height between the top and bottom of the cabinet or bookcase.
  2. Enter how many shelves go inside that opening.
  3. Enter the shelf thickness (often 3/4 inch).
  4. Read the even gap, then use the shelf positions to lay out pin holes or dados from the bottom up.

Example: 3 shelves of 3/4 inch stock in a 36 inch opening gives an even gap of about 8 7/16 inches, with shelf bottoms at roughly 8 7/16, 17 5/8, and 26 13/16 inches from the floor of the opening.

Shelf Spacing Calculator FAQ

Shelf Spacing Calculatorquestions.

  • How do you evenly space shelves?

    Subtract the combined thickness of the shelves from the opening height, then divide by the number of gaps, which is the number of shelves plus one. That gives the equal space between each shelf and at the ends.

  • Should shelf spacing include the shelf thickness?

    Yes. The shelves themselves take up height, so even spacing is figured on the clear space left after removing the total shelf thickness. This calculator does that for you.

  • What is a good shelf spacing?

    It depends on what is stored. Common references are about 8 to 10 inches for paperbacks, 10 to 12 inches for larger books, and 12 to 15 inches for display items. Set the number of shelves to land near the spacing you want.

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