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Shelf Spacing Helper

Plan shelf layouts with even gaps or maximum shelves by gap size

Unit System & Presets
Cabinet Dimensions
Enter the interior measurements of your cabinet or bookcase
Spacing Method
Choose how you want to calculate shelf positions
Optional Settings
When enabled, gaps are distributed evenly including the space below the first shelf. For N shelves, creates N+1 equal gaps (recommended for realistic cabinet spacing).

Enter Cabinet Dimensions

Fill in the interior height and shelf thickness to calculate shelf positions

Calculation Methods
Even gaps: G = (H - B - T - N×t) / N
Max shelves: N = floor((H - B - T) / (t + S_target))
Legend: H=height, B=bottom, T=top, N=shelves, t=thickness, G=gap

About the Shelf Spacing Helper

This shelf-spacing calculator works out the vertical positions for a set of shelves within a cabinet or bookcase, and lines them up with a drilling system such as the 32 mm cabinet-making standard. It gives you even, repeatable spacing and a list of hole positions to mark or jig.

Dividing the height

Given the internal height and the number of shelves, the calculator divides the available space into equal openings, allowing for shelf thickness so the visible gaps — not just the centre lines — come out equal. You can also bias the layout, for example making the bottom opening taller for larger books or appliances, while keeping the rest even.

If you drill for adjustable shelf pins, positions are usually snapped to a regular hole pitch (commonly 32 mm, the System 32 standard) so a single drilling jig serves every cabinet and shelves can be moved later.

Fixed versus adjustable shelves

Fixed shelves in dadoes give maximum strength and are spaced exactly where you want them. Adjustable shelves on pins trade a little strength for flexibility and must land on the drilled hole pitch. Deciding which you want before you mark out avoids holes that do not line up with the spacing you intended.

Worked example

A bookcase has 900 mm of internal height for 3 shelves that are 18 mm thick, with equal openings.

  1. Total shelf thickness = 3 × 18 = 54 mm.
  2. Remaining open space = 900 − 54 = 846 mm.
  3. 4 openings (above, below, and between shelves) = 846 ÷ 4 ≈ 211.5 mm each.

Each opening is about 211 mm; position the shelves so those gaps stay equal.

Frequently asked questions

What is the 32 mm shelving system?

System 32 is a cabinet-making standard where holes for shelf pins, hinges, and hardware are drilled on a 32 mm vertical pitch. Snapping shelf positions to this pitch means one jig and one set of hardware fit every cabinet.

Does the calculator allow for shelf thickness?

Yes. It subtracts the combined thickness of the shelves from the internal height before dividing, so the visible openings are equal rather than the centre lines.

Can I make one opening taller than the rest?

Yes — set a larger bottom (or top) opening for tall items and the calculator keeps the remaining openings even.