Cut list optimizer· 3 min read
Raised Garden Bed from Boards: How Many Boards to Buy and How to Cut Them
A 2 × 1 m raised bed three boards high: the cut list, why a 4 m board won't give you two 2 m sides, and how many boards to buy for the least waste.
A 2 × 1 m raised bed (about 6.5 × 3.3 ft) looks simple: a few boards, four corner posts, screws. Then the store has boards 3 m and 4 m long and it is no longer obvious how many to take. Let's work it out on a real example — including one trap a lot of people fall into.
The brief
- Outside size of the bed 2,000 × 1,000 mm.
- Boards 28 mm thick and 150 mm wide, 3 rows high — the bed is 3 × 150 = 450 mm tall.
- Long boards run the full 2,000 mm, short ones fit between them: 1,000 − 2 × 28 = 944 mm.
- Inside each corner a 50 × 50 mm post, 450 mm long, that the boards screw into.
- Kerf 3 mm (circular saw), 5 mm squaring cut at the start of every board.
In total you need 6 boards of 2,000 mm and 6 boards of 944 mm — two long and two short sides in each of the three rows.
The trap: a 4 m board does not give two 2 m sides
The first idea is usually “buy 4 m boards and cut each in half”. But two 2,000 mm pieces with a squaring cut and one cut between them need 5 + 2,000 + 3 + 2,000 = 4,008 mm. The board is 4,000 mm, so the second piece would be 8 mm short. As a result each 4 m board yields only one long side and two short ones.
| Purchase | Length bought | Waste |
|---|---|---|
| 6 × 3,000 mm | 18,000 mm | 1.9 % |
| 6 × 4,000 mm (4 m boards only) | 24,000 mm | 26.4 % |
| 5 × 4,000 mm with the bed 1,990 mm long | 20,000 mm | 12 % |
With 3 m boards there is almost no waste: each one gives one long and one short side. If the store only has 4 m boards, make the bed 1,990 mm long — two long sides then fit in one board and you save a whole board.
To put it in perspective: all the pieces add up to 17,664 mm. Six 3 m boards are 18,000 mm, so only 336 mm of wood goes to sawdust, squaring cuts and offcuts.
The cut list
- 16 boards of 3,000 mm: 2,000 + 944 mm from each.
- 2Each board leaves a 45 mm offcut — after the squaring cut and both kerfs.
- 3Corner posts: 4 × 450 mm from one 2,000 mm post, leaving 183 mm.
The posts have a different cross-section from the boards, so plan them as a separate cut list in the calculator. If you want to sink them into the ground, add the depth to their length and run it again.
Cut list optimizerOpen this example in the cut list calculatorIf you want a different size
The rule from the example holds in general: a piece that is “exactly half” the board length will not fit twice, because the squaring cut and the kerf take something. For a 1.5 × 1 m bed, for instance, a 3 m board would not give two long sides of 1,500 mm either. Enter the sizes before you go shopping — a few millimetres on the bed length often decide a whole board.
Workshop tips
- Measure the real board thickness before cutting — the short sides depend on it. For anything other than 28 mm, recompute 1,000 − 2 × thickness.
- Cut all the long pieces first, then the short ones. Measure the short sides off the first assembled row.
- Alternate the corner joints so a long board always covers the end of a short one — the frame holds together better.
- The 183 mm post offcut makes a handy spacer when screwing on the next rows.