Shelf spacing calculator
Space shelves evenly inside a cabinet or bookcase from its internal height and shelf thickness, by shelf count or by the largest gap you want. Optionally snap each shelf to the nearest pin hole.
Internal height above 0 and up to 5 m, shelf thickness up to 200 mm, 1 to 100 shelves, clear spaces up to 5 m, pin hole spacing up to 500 mm. Calculated on your device; download a JSON report and CSV files of results and shelf positions. This calculator uses the measurement fields only. Results update as you type. Up to 1,000,000 characters.
Your result
How to use Shelf spacing calculator
- Choose the unit and enter the internal height and the shelf thickness.
- Choose whether to plan by number of shelves or by the largest gap.
- Add clear space at the bottom or top if part of the height must stay free.
- Enter the pin hole spacing and first hole height to snap shelves, or leave the spacing empty, then download the positions.
Useful next steps
Equal gaps
Shelves share the height between the clear spaces, so every gap below, between and above them is the same: gap = (height − shelves × thickness) ÷ (shelves + 1). For an 1,800 mm cabinet with four 18 mm shelves, each gap is 345.6 mm and the first shelf underside sits 345.6 mm above the base.
Planning by the largest gap
In largest-gap mode the calculator finds the fewest shelves that keep every equal gap at or below your limit. A 72 in bookcase with 0.75 in shelves, 4 in kept clear at the bottom and a 12 in limit needs 5 shelves with gaps of about 10.71 in. Snapping to pin holes can then push one gap above your limit; the report warns you when that happens.
Snapping to pin holes
Shelf-pin cabinets drill holes at a fixed pitch, commonly 32 mm in the 32 mm cabinetmaking system (Wikipedia, checked 16 October 2026). Each shelf moves to the nearest hole centre and the table shows the shift and the new gaps. With 32 mm holes starting at 32 mm, the example gaps become 334 to 366 mm.
Limits
Internal heights up to 5 m, shelves up to 200 mm thick and up to 100 shelves. Positions are measured from the top of the base. Pin and support sizes are not modelled; a layout whose snapped shelves would overlap is rejected.