People type this into search every day: shelving calculator.
The order is a length of board and a count of brackets. Sag, wall type, and the load rating on the bracket are a different check. This page follows the shelving material calculator.
Total length, plus the waste you type, then whole boards
The calculator assumes offcuts can be reused from one shelf to the next. It does not lay the cuts out on a drawing.
linear metres = shelves × length per shelf × (1 + waste ÷ 100)
boards = ceiling of (linear metres ÷ stock board length)
brackets = ceiling of (shelves × brackets per shelf)
On a US display the linear metres become feet. The inputs stay in metres. Brackets are a count, so they do not convert.
Fig 1
Shelf length into stock boards
Waste is added before the boards are counted
Linear board is shelves times length, then the waste percent. Boards are that length divided by the stock board, rounded up. Brackets are shelves times brackets per shelf.
The waste percent is a planning allowance you type. The default is 10%. Nothing in the formula looks up a span table. The note on the calculator says to check fastener and bracket load ratings before you install. The board feet post is the volume of those boards once you know thickness and width. This tool stops at length and a bracket count. The decking post is the outdoor cousin: rows across a width, then waste. The flooring post is area, then packs.
Example 1: six shelves, the published defaults
- shelves: 6
- length per shelf: 1.2 m
- stock board length: 2.4 m
- brackets per shelf: 3
- cutting waste: 10%
Before waste: 6 × 1.2 = 7.2 m
With 10% waste: 7.2 × 1.10 = 7.92 m, which displays as 26 ft
Boards: ceiling of 7.92 ÷ 2.4 = ceiling of 3.3 = 4
Brackets: 6 × 3 = 18
Four boards are 9.6 m. The order is 7.92 m, so 1.68 m of that fourth board is past the length the formula asked for. You still buy the fourth board, because 3 × 2.4 m = 7.2 m and 7.2 is short of 7.92.
Calculator result
Shelving material
- Number of shelves
- 6 shelves
- Length per shelf
- 1.2 m
- Stock board length
- 2.4 m
- Brackets per shelf
- 3 brackets
- Cutting waste
- 10%
4 boards
stock boards to buy
- Required board length
- 26 ft
- Brackets
- 18
The 7.2 m of shelves displays as 23.6 ft. Waste is 26 − 23.6 = 2.4 ft. That is 2.4 ÷ 26 = 9.2% of the length you are shown, because 10% was applied to the 7.2 m and the feet are rounded. The other 90.8% is the six shelves.
Fig 2 · 1/2
26 ft, shelves and waste
Six shelves at 1.2 m, 10% waste
Shelves
23.6 ft
Waste
2.4 ft
The six shelves are 23.6 ft before waste.
10% waste adds 2.4 ft. The length to cover is 26 ft.
Example 2: a closet, four shorter shelves
- shelves: 4
- length per shelf: 0.8 m
- stock board: 2.4 m
- brackets per shelf: 2
- waste: 10%
Before waste: 4 × 0.8 = 3.2 m
With waste: 3.2 × 1.10 = 3.52 m, displayed as 11.5 ft
Boards: ceiling of 3.52 ÷ 2.4 = ceiling of 1.47 = 2
Brackets: 4 × 2 = 8
Calculator result
Shelving material
- Number of shelves
- 4 shelves
- Length per shelf
- 0.8 m
- Stock board length
- 2.4 m
- Brackets per shelf
- 2 brackets
- Cutting waste
- 10%
2 boards
stock boards to buy
- Required board length
- 11.5 ft
- Brackets
- 8
One 2.4 m board is 7.87 ft, which is short of 11.5 ft, so the ceiling adds the second board. Two shelves of 0.8 m fit on one stock board with room left, and the waste does not push you to a third board. 3.52 ÷ 2.4 stays under 2.
Example 3: a long wall where each shelf matches the stock
- shelves: 8
- length per shelf: 2.4 m
- stock board: 2.4 m
- brackets per shelf: 4
- waste: 15%
Before waste: 8 × 2.4 = 19.2 m, which is exactly 8 boards.
With 15% waste: 19.2 × 1.15 = 22.08 m, displayed as 72.4 ft
Boards: ceiling of 22.08 ÷ 2.4 = ceiling of 9.2 = 10
Brackets: 8 × 4 = 32
Calculator result
Shelving material
- Number of shelves
- 8 shelves
- Length per shelf
- 2.4 m
- Stock board length
- 2.4 m
- Brackets per shelf
- 4 brackets
- Cutting waste
- 15%
10 boards
stock boards to buy
- Required board length
- 72.4 ft
- Brackets
- 32
The waste is 2.88 m, about two extra stock lengths, and the ceiling rounds 9.2 up to 10. If you had typed 0% waste, the same wall would be 8 boards and the same 32 brackets. The 15% field is the whole reason the order moves from 8 boards to 10. A shelf that matches the stock length is not a one-board shelf once waste is in the formula. Example 7 puts that on a single shelf.
Example 4: what if I change only the waste
Keep 6 shelves, 1.2 m each, a 2.4 m stock board, and 3 brackets. Brackets stay at 18. Only the length and the board count can move.
| Waste | Linear metres | Displayed | Boards |
|---|---|---|---|
| 0% | 7.20 | 23.6 ft | 3 |
| 5% | 7.56 | 24.8 ft | 4 |
| 10% | 7.92 | 26 ft | 4 |
| 15% | 8.28 | 27.2 ft | 4 |
| 20% | 8.64 | 28.3 ft | 4 |
At 0% the length is exactly 3 boards. At 5%, 7.56 ÷ 2.4 = 3.15, and the ceiling jumps to 4. From 5% through 20% you are still on 4 boards, while the length you have to cover grows from 24.8 ft to 28.3 ft. The fourth board absorbs that growth until the length passes 9.6 m.
From the 10% default to 20% you add 28.3 − 26 = 2.3 ft of required length and zero boards. From 0% to 5% you add 1.2 ft and a whole board.
Fig 3 · 1/5
Required length as waste grows
Six shelves at 1.2 m. Brackets stay at 18.
Required board length (ft)
- Length
| Point | Length |
|---|---|
| 0% | 23.6 |
| 5% | 24.8 |
| 10% | 26 |
| 15% | 27.2 |
| 20% | 28.3 |
At 0% waste the length is 23.6 ft, exactly 3 boards.
At 10% it is 26 ft. At 20% it is 28.3 ft, still 4 boards.
Example 5: what if I change the stock length
Keep the six shelves, the 1.2 m length, the 10% waste, and the 3 brackets. Required length stays 7.92 m, displayed as 26 ft. Brackets stay 18. Only the board count changes.
| Stock board | Boards | Length left on the last board |
|---|---|---|
| 1.8 m | 5 | 1.08 m left on the fifth |
| 2.4 m | 4 | 1.68 m left on the fourth |
| 3.6 m | 3 | 2.88 m left on the third |
The working:
- 7.92 ÷ 1.8 = 4.4, ceiling 5. Five boards are 9.0 m.
- 7.92 ÷ 2.4 = 3.3, ceiling 4. Four boards are 9.6 m.
- 7.92 ÷ 3.6 = 2.2, ceiling 3. Three boards are 10.8 m.
A longer stock board is a smaller count, and it leaves more unused length on the last piece. The formula does not price that offcut. It only stops you buying a board count that is short of 7.92 m.
Fig 4 · 1/3
Boards at three stock lengths
The required length stays 26 ft
- Boards
| Category | Boards |
|---|---|
| 1.8 m | 5 |
| 2.4 m | 4 |
| 3.6 m | 3 |
A 2.4 m stock board is the 4-board default.
A 1.8 m board needs 5. A 3.6 m board needs 3.
Example 6: brackets do not change the board count
Same six shelves, same 1.2 m, same 2.4 m stock, same 10% waste. Boards stay at 4. Length stays at 26 ft.
| Brackets per shelf | Brackets to buy |
|---|---|
| 2 | 12 |
| 3 | 18 |
| 4 | 24 |
The bracket line is shelves × brackets per shelf, then a ceiling. With whole numbers the ceiling does nothing: 6 × 3 = 18. Adding a bracket per shelf adds 6 brackets and zero boards. The formula will not tell you whether 2 brackets can carry the span. That is the load rating on the bracket and the wall you are fixing to. Type the count you mean to install.
Example 7: the common mistake, one board per shelf
The tool’s assumption is that offcuts move from shelf to shelf. The default shows what that is worth.
Each 1.2 m shelf, with 10% waste, wants 1.32 m. A 2.4 m board can hold one of those cuts. It cannot hold two, because 1.32 × 2 = 2.64 m, and 2.64 is longer than 2.4. If you refuse to reuse the offcut, you buy 6 boards. The calculator, reusing offcuts, buys 4. The gap is 2 boards on this one run.
Without waste the picture is kinder. Two 1.2 m shelves fit on one 2.4 m board exactly, so 6 shelves are 3 boards. That is the 0% row in Example 4. The mistake people make next is to keep that 3-board count after they have typed 10% waste. At 10% the length is 7.92 m, and 3 boards are 7.2 m. You are 0.72 m short, which is the 2.4 ft of waste in the figure above.
A single shelf that matches the stock length makes the same point in a smaller order.
- shelves: 1
- length: 2.4 m
- stock: 2.4 m
- brackets: 3
- waste: 10%
Linear: 2.4 × 1.10 = 2.64 m, displayed as 8.7 ft
Boards: ceiling of 2.64 ÷ 2.4 = ceiling of 1.1 = 2
Brackets: 3
The shelf equals the board you are buying, and the waste still calls for a second board. Set waste to 0% and this one shelf is 1 board. Leave it at 10% and it is 2.
Example 8: a pantry of short shelves, and five shelves at 1.5 m
Pantry, ten shelves:
- shelves: 10
- length: 0.9 m
- stock: 2.4 m
- brackets per shelf: 2
- waste: 12%
Before waste: 10 × 0.9 = 9 m
With waste: 9 × 1.12 = 10.08 m, displayed as 33.1 ft
Boards: ceiling of 10.08 ÷ 2.4 = ceiling of 4.2 = 5
Brackets: 10 × 2 = 20
Five boards are 12 m. You need 10.08 m, so the fifth board is partly spare. Four boards are 9.6 m, which is short of 10.08 m.
If each 0.9 m shelf is cut from its own board, you buy 10. Two shelves of 0.9 m, even after 12% waste (1.008 m each), still fit on a 2.4 m board. The reuse assumption is doing real work here: 5 boards against a no-sharing count of 10.
Five shelves at 1.5 m, 2.4 m stock, 3 brackets, 10% waste:
Before waste: 5 × 1.5 = 7.5 m
With waste: 7.5 × 1.10 = 8.25 m, displayed as 27.1 ft
Boards: ceiling of 8.25 ÷ 2.4 = ceiling of 3.44 = 4
Brackets: 15
Each shelf with waste wants 1.65 m. That fits on one 2.4 m board, and two of them do not (3.3 m). A no-sharing cut list is 5 boards. The calculator’s shared-offcut count is 4. One board is the whole difference, on a run of five shelves.
The orders next to each other
| Example | Shelves | Length | Stock | Waste | Brackets each | Boards | Linear | Brackets |
|---|---|---|---|---|---|---|---|---|
| 1. Defaults | 6 | 1.2 m | 2.4 m | 10% | 3 | 4 | 26 ft | 18 |
| 2. Closet | 4 | 0.8 m | 2.4 m | 10% | 2 | 2 | 11.5 ft | 8 |
| 3. Long wall | 8 | 2.4 m | 2.4 m | 15% | 4 | 10 | 72.4 ft | 32 |
| 4. No waste | 6 | 1.2 m | 2.4 m | 0% | 3 | 3 | 23.6 ft | 18 |
| 4. 5% waste | 6 | 1.2 m | 2.4 m | 5% | 3 | 4 | 24.8 ft | 18 |
| 4. 20% waste | 6 | 1.2 m | 2.4 m | 20% | 3 | 4 | 28.3 ft | 18 |
| 5. Short stock | 6 | 1.2 m | 1.8 m | 10% | 3 | 5 | 26 ft | 18 |
| 5. Long stock | 6 | 1.2 m | 3.6 m | 10% | 3 | 3 | 26 ft | 18 |
| 6. Two brackets | 6 | 1.2 m | 2.4 m | 10% | 2 | 4 | 26 ft | 12 |
| 6. Four brackets | 6 | 1.2 m | 2.4 m | 10% | 4 | 4 | 26 ft | 24 |
| 7. One full shelf | 1 | 2.4 m | 2.4 m | 10% | 3 | 2 | 8.7 ft | 3 |
| 7. No shared offcut | 6 | 1.2 m | 2.4 m | 10% | 3 | 6 | 18 | |
| 8. Pantry | 10 | 0.9 m | 2.4 m | 12% | 2 | 5 | 33.1 ft | 20 |
| 8. Five at 1.5 m | 5 | 1.5 m | 2.4 m | 10% | 3 | 4 | 27.1 ft | 15 |
Open the shelving material calculator with the shelf count, the length of one shelf, the board your yard sells, and a waste percent you are willing to carry home. Then take the board count to the lumber board feet calculator if you want the volume, and the room area calculator if you are still sizing the wall those shelves sit on. Bracket ratings stay on the hardware, not in this length.