Easy Wood Calc

Cut list for a 30 in wide bookcase from 1×12 boards

Short answer

A 36 in tall, 30 in wide bookcase built from 1×12s takes 2 × 1×12 boards, 8 ft long. The shelves sit between the ¾ in sides, so cut them 28-1/2 in, not 30 in: each board gives one 36 in side and two shelves, with about 2-5/8 in left over.

How to work it out

  1. Shelf length = outside width − 2 × side thickness = 30 in − 2 × 3/4 in = 28-1/2 in
  2. 2 × 36 in + 4 × 28-1/2 in = 15.5 ft of parts, packed to fill each board as full as it will go → 2 boards (3% offcut and kerf)

A first bookcase: two sides, a top, a bottom and two shelves, all from 1×12 boards that are really ¾ × 11¼ in. The top and bottom sit between the sides like the shelves, so the case is 36 in tall overall.

Adjust for your project

Buying rough hardwood by the board foot? Switch to the rough-stock takeoff.
Pieces
2 rows
One row per length; fractions work (28 1/2). Shelves that sit between the sides: outside width − 2 × side thickness — 30 − 2 × 3/4 = 28 1/2.
in
Works out the length of shelves that fit between the sides. Copy it into the pieces above.
in
1× boards and ¾ plywood: 3/4 in (¾ plywood is really 23/32).
in
Type 8' or 96 — 8 ft = 96 in · 10 ft = 120 · 12 ft = 144.
Only labels the shopping list — the cutting math is the same for any width.
More options: Kerf · Trim · Price per board (optional)
in
The sliver of wood each cut turns to sawdust. Most saws: 1/8 in.
in
Cut off once per board if the factory ends are split or out of square.
$
What to buy2 × 1×12 boards, 8 ft long
Shelves between the sides: cut them
28-1/2 in
Boards needed
2 boards · 1×12
Pieces placed
6 pieces
Offcut and kerf waste
3%
Total length of pieces
15.5 ft
Where to cut each board
BoardsCut these lengths (in)Offcut left
2 boards36 + 28-1/2 + 28-1/2about 2-5/8 in
  • Anchor it. A freestanding bookcase can tip over when a child climbs it or the top shelves are loaded. Fasten the top to a wall stud with an anti-tip strap or bracket — drywall anchors alone won’t hold it.

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Speed square (7 in)For a handful of cuts, a speed square guides a circular saw square across the board and marks every line in one move.
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Boards for the same bookcase, by board length

Boards for the same bookcase, by board length
Board lengthBoards neededOffcut and kerf waste
6 ft (72 in)3 boards14%
8 ft (96 in)2 boards3%
10 ft (120 in)2 boards23%
12 ft (144 in)2 boards35%

What to know about cutting a 30 in bookcase

The easy mistake is cutting the shelves to the width you want the case to be. Every shelf sits between two ¾ in sides, so it is 1½ in shorter than the outside width: 30 − 2 × ¾ = 28½ in. Shelves cut 30 in long make a case 31½ in wide — fine on its own, but not in a 30 in alcove.

With four 28½ in pieces (top, bottom and two shelves) the openings are 11 in tall: 36 in of side, less four ¾ in boards, leaves 33 in, split three ways. Measure your tallest books before you fix the shelves; if they won’t fit, make one opening taller and the others shorter — the cut list stays the same.

Two 8 ft 1×12s cover it. The calculator puts a 36 in side and two shelves on each board — 93 in of wood plus two kerfs — leaving about 2-5/8 in. Packing the boards longest-first would put both sides on one board and need a third, so lay the cuts out the way the table shows. Pick straight boards with tight knots, and keep any knot away from the middle of a shelf, where it bends most.

A ¼ in plywood back, about 30 × 36 in, squares the case and stops it racking; it comes out of one 4 × 8 sheet with plenty left. A 28½ in pine shelf carrying a full row of books stays inside the usual sag guideline — check yours on Will a 1x12 pine shelf sag over 36 inches, which shows why the full 36 in width would struggle.

Fasten the finished case to the wall: a strap or bracket from the top into a wall stud keeps a loaded bookcase from tipping onto someone. For the kerf arithmetic behind the offcuts, see How many 24 in pieces from an 8 ft board.

Different size? Use the full Cut List Calculator.

What you’ll need

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Frequently asked questions

What length are the shelves for a 24 in wide bookcase?

22-1/2 in — 24 in minus two ¾ in sides. With 36 in sides the case still takes 2 × 1×12 boards, 8 ft long.

How many 8 ft 1x12s for a 48 in tall, 30 in wide bookcase with five shelves?

3 boards. Each 48 in side shares a board with one 28½ in shelf, and the other three shelves come out of the third board.

Other common sizes

Sources