Construction & DIY · Woodworking
Shelf spacing calculator.
Enter the inside height, the shelf thickness and how many shelves you want to see the equal opening height and where each shelf sits.
Inputs
Shelf layout
Enter a height, thickness and shelf count.
How do you space shelves evenly?
With n shelves between a fixed bottom and top there are n + 1 openings. The shelves use up n times their thickness, so each equal opening is (inside height − n × thickness) / (n + 1). The underside of shelf k sits at k openings plus (k − 1) thicknesses from the bottom, and its top surface is one thickness higher.
Worked example. A 72 in inside height with five 3/4 in shelves leaves 72 − 3.75 = 68.25 in of opening, shared by six openings: 11.375 in each (11 3/8 in). The first shelf's underside is at 11.375 in and its top at 12.125 in.
Use the optional minimum opening to see the most shelves that still leave that clear space. Uneven spacing is fine for books of different heights; this tool is for equal spacing. To check the shelves will not bend under the load, use the shelf sag calculator.
Frequently asked questions
How do I calculate equal spacing between shelves?
Subtract the total shelf thickness from the inside height, then divide by the number of shelves plus one. For 72 in inside height and five 3/4 in shelves, each opening is 11.375 in.
Is the height inside the cabinet or the overall height?
Use the inside height between the top surface of the bottom panel and the underside of the top panel. If you only have the overall height, subtract the thickness of the top and bottom panels.
How many shelves fit in a bookcase?
Enter the smallest opening you will accept. The tool gives the most equal shelves that still leave at least that opening.
Will the shelves sag?
Spacing does not affect sag; span, thickness, material and load do. Use the shelf sag calculator for that.
Sources
Checked
No published data table is used; this is arithmetic on the inside height, tested for the opening formula, the shelf positions and the maximum shelf count. Runs entirely in your browser. Nothing you type is sent or stored.
Scope
Layout arithmetic for woodworking. Check the layout against your own drawing before cutting.