Shelf Spacing Calculator
Divide a bookcase, cabinet, or closet into equal shelf openings. Get the clear opening, the shelf-to-shelf spacing, and a mark for every shelf measured from the bottom.
Enter the layout
How much wood do I need? Material estimate
5 shelves × 30" = 12.5 linear ft · 8.79 board feet
Board feet use the actual sizes entered here. Open in the board foot calculator to add waste, other parts, tax, and a shareable shopping list.
How to lay out shelves with equal openings
Measure the inside height
Measure from the top face of the fixed bottom to the underside of the fixed top. That clear inside height is the span. Do not include the thickness of the case bottom or top; they are not part of the layout. If the case has a toe kick or a face frame rail that overlaps the opening, decide whether you want equal openings behind the face frame or equal openings as seen from the front, and measure that space.
Enter the real shelf thickness
Use the measured thickness of the shelf material. A sheet sold as ¾-inch plywood often measures closer to 23/32 inch, and solid wood shelves may be a full inch. Small differences matter more than you might expect: five shelves that are each 1/32 inch thicker than you assumed take away 5/32 inch from the openings.
Choose the end condition
For shelves between a fixed bottom and top, choose equal outer gaps. Four shelves then create five equal openings: one below the first shelf, three between shelves, and one above the last. Choose flush outer edges only when the first and last "shelves" are themselves the bottom and top of the layout, for example when you are dividing a tall opening that has no fixed panels.
Read the results
The large number is the clear opening between shelves. The on-center spacing is the distance from one shelf's top to the next shelf's top, which is the opening plus one shelf thickness. Open the list of marks to get each shelf's height from the inside bottom to its underside. Drill shelf-pin holes or set cleats at those marks.
Worked bookcase example
A bookcase has an inside height of 72 inches and will hold five ¾-inch shelves between a fixed bottom and top. The shelves take 3¾ inches, leaving 68¼ inches. With equal outer gaps there are six openings, so each opening is 68¼ ÷ 6 = 11⅜ inches. The first shelf's underside sits 11⅜ inches above the bottom, the second at 23½ inches, and so on in steps of 12⅛ inches.
Plan for what will sit on the shelves
Equal openings look calm, but storage rarely has equal heights. A common approach is to use a larger opening at the bottom for heavy or tall items and equal openings above it. To do that, calculate the bottom opening first, subtract it and one shelf thickness from the inside height, then use the calculator for the remaining shelves. Add about an inch above the tallest item so you can tip it in and out.
Typical starting points: 10 to 13 inches for most books, 14 to 16 inches for binders and large books, about 9 to 11 inches inside kitchen upper cabinets, and 6 to 8 inches for folded clothes or shoe cubbies. These are only starting points; measure what you will store.
Adjustable shelves and shelf pins
For adjustable shelves, drill a row of holes on a regular pitch, often 32 mm or 1¼ inches, instead of at single marks. Use the calculator to find where the shelves will start, then center the hole row so that those positions fall on or near a hole. A shelf-pin jig keeps the holes in the left and right rows at the same heights so shelves sit level.
Shelf sag
Spacing does not change how much a shelf sags, but span and load do. Long shelves loaded with books can bow over time, especially in particleboard. Keep spans short, add a hardwood edge strip, or add a center support for long, heavily loaded shelves.
For other layouts, see the equal spacing calculator for hooks, balusters, and boards, and the drawer box calculator for drawers in the same cabinet.
Shelf Spacing Calculator FAQ
How do I space shelves evenly?
Subtract the total thickness of all shelves from the inside height, then divide by the number of openings. With shelves floating between a fixed bottom and top there is one more opening than shelves.
What is a standard shelf spacing?
Bookcases commonly use openings of about 10 to 13 inches for paperbacks and standard books and 14 to 16 inches for large books and binders. Kitchen upper cabinets often use about 9 to 11 inches. Measure the tallest item you plan to store and add an inch or so for clearance.
Should I include the top and bottom panels?
No. Measure the inside height between the fixed bottom and the fixed top, and count only the adjustable or added shelves. The calculator then gives equal openings above, between, and below them.
What do the shelf marks measure?
Each mark is the distance from the inside bottom to the underside of a shelf. That is where a shelf pin, cleat, or dado edge goes.
How thick are shelves?
Plywood and melamine shelves are usually about ¾ inch thick; solid wood shelves can be ¾ to 1 inch. Measure the actual material, because nominal ¾-inch plywood is often slightly thinner.