Quick answers
- 1 1/4' x 3' pieces from a 3' x 9' sheet: 7. The 3 ft side matches the sheet width, so the pieces run in one row: 9 / 1.25 = 7.2, so 7.
- 1 1/4' x 4' pieces from a 4' x 8' sheet: 6. 8 / 1.25 = 6.4, so 6, with or without a kerf.
- 24 x 30 in pieces from a 4x8: 6 on paper, 3 on a table saw. Two 24-inch rows and a 1/8-inch kerf need 48 1/8 inches.
- 2 x 4 ft pieces from a 4x8: 4 on paper, 3 on a table saw. Four need 96 3/8 inches along the sheet.
Sizes in feet can go straight into the calculator in the in / ft mode: type 1 1/4' or 3 ft. Solving a math problem that ignores the saw blade? Set the kerf to 0.
Why dividing the areas gives the wrong answer
The quick way to estimate is to divide the area of the sheet by the area of one part. A 4x8 sheet is 4,608 square inches and a 12 x 12 square is 144, so the answer looks like 32. On a table saw it is 21.
Every cut removes the width of the blade, about 1/8 inch. Eight 12-inch squares along the 96-inch side need 96 inches of parts and seven kerfs between them, 96 7/8 inches in all, so only seven fit. Across the 48-inch side, four squares need 48 3/8 inches, so only three fit. 7 x 3 = 21, and a third of the sheet is waste.
The same thing happens with every part that divides the sheet exactly: 24 x 24, 24 x 48, 16 x 24, 12 x 24. These sizes are popular because they divide a 4x8 evenly - but only on paper, where the blade removes nothing. That is why the calculator opens on 24 x 48: four by area, three on a real sheet.
If the parts can lose 1/8 inch, cut them that much undersize. At 11 7/8 x 11 7/8 all 32 squares fit, and at 23 7/8 x 48 all four quarter-sheets do.
How to count pieces by hand
- Add one kerf to the sheet length and one kerf to the part length, divide, and round down. That is how many fit along the sheet.
- Do the same with the widths. That is how many fit across.
- Multiply the two.
- Turn the part 90 degrees, repeat steps 1-3, and keep the larger number.
The kerf added to the sheet length is there because the last part needs no cut after it. For 1 1/4 x 3 ft pieces on a 3 x 9 ft sheet with a 1/8-inch kerf: along the sheet, 108.125 / 15.125 = 7.15, so 7; across, 36.125 / 36.125 = 1; 7 x 1 = 7.
When mixing orientations fits more
A straight grid, in either orientation, is not always the best layout. Take a 16 x 24 inch part on a 4x8 with a 1/8-inch kerf. With the 24-inch side along the sheet, three fit along and two across: 6. Turned, five fit along and only one across, because two 24-inch rows need 48 1/8 inches: 5. Laid out with some parts one way and some the other, the same sheet gives 8.
The calculator tries every way to split the sheet into two blocks, along its length and across it, with the part one way in one block and turned 90 degrees in the other. A plain grid is the case where one of the blocks is empty. It then draws the best layout and colors the turned parts green, so you can see where the extra parts came from.
If your material has a grain or a print that must run one way, check the grain box: every part keeps its length along the sheet's length, and the count can drop.
Pieces per 4x8 sheet: common sizes
With a 1/8-inch (3.2 mm) kerf and no edge trim:
| Part | Pieces per 4x8 | By area alone |
|---|---|---|
| 12 x 12 in | 21 | 32 |
| 11 7/8 x 11 7/8 in | 32 | 32 |
| 16 x 16 in | 10 | 18 |
| 16 x 24 in | 8 | 12 |
| 12 x 24 in | 10 | 16 |
| 24 x 24 in | 3 | 8 |
| 24 x 30 in | 3 | 6 |
| 24 x 48 in | 3 | 4 |
| 15 x 48 in (1 1/4 x 4 ft) | 6 | 6 |
| 600 x 300 mm on 2440 x 1220 | 16 | 16 |
| 500 x 500 mm on 2440 x 1220 | 8 | 11 |
A part that divides the sheet exactly is the worst case: the kerf costs a full row. Metric parts that leave a few millimeters spare, like 600 x 300 on a 2440 x 1220 sheet, lose nothing to it.
More than one part size
This page answers the question for one part size. For a cut list with several sizes, such as cabinet sides, shelves, backs and doors, the full optimizer packs them together across as many sheets as it takes and prints the cut sequence and part labels. The Open this layout in the full optimizer link under the calculator carries over your part, sheet, kerf and trim, with the quantity set to the count that fits. For the number of sheets a whole project needs, see the plywood calculator.
Edge trim
Factory edges are often chipped or not quite square, so many shops trim 5-10 mm (about 1/4 inch) off each edge before cutting parts. Enter that as the edge trim, and the calculator takes it off all four edges before counting: a 96 x 48 sheet with a 1/4-inch trim is counted as 95 1/2 x 47 1/2. It can cost a row too: 600 x 300 mm parts drop from 16 to 12 per sheet once 10 mm comes off each edge.
FAQ
How many 1 1/4 ft by 3 ft pieces can you cut from a 3 ft by 9 ft sheet of plywood?
Seven. The 3 ft side of each piece matches the 3 ft width of the sheet, so the pieces sit in one row along the 9 ft length: 9 / 1.25 = 7.2, rounded down to 7. Seven pieces use 105 of the 108 inches, and the 3 inches left over (2 1/8 after the seven 1/8-inch saw cuts that free the pieces) are too narrow for an eighth piece.
How many 1 1/4 ft by 4 ft pieces can you cut from a 4 ft by 8 ft sheet of plywood?
Six. The 4 ft side of each piece matches the 4 ft width of the sheet, so the pieces run in one row along the 8 ft length: 8 / 1.25 = 6.4, rounded down to 6. A 1/8-inch kerf does not change it: six pieces and five kerfs take 90 5/8 inches of the 96.
How many 24x30 pieces can you get from a 4x8 sheet of plywood?
Six on paper, three on a table saw. With the 30-inch side along the sheet, three fit along and two across, but two 24-inch rows and a 1/8-inch kerf need 48 1/8 inches, and the sheet is 48. Make the pieces 23 7/8 x 30 and all six fit.
How many 2x4 pieces can you get from a 4x8 sheet of plywood?
Four quarter-sheets of 24 x 48 inches by area, but three with a real blade. Four 24-inch widths plus three 1/8-inch kerfs need 96 3/8 inches along the 96-inch length, so the fourth piece ends up 23 5/8 inches wide. Four fit if they can be 23 7/8 x 48.
How many 12x12 pieces can you cut from a 4x8 sheet of plywood?
21 with a 1/8-inch kerf, not the 32 that dividing the areas gives. Eight 12-inch squares need 96 7/8 inches along the sheet, so only seven fit, and four need 48 3/8 inches across it, so only three fit: 7 x 3 = 21. Cut the squares at 11 7/8 inches and all 32 fit.
Why does the calculator give fewer pieces than my math?
Because the saw blade turns part of the sheet into sawdust - about 1/8 inch per cut - and parts that divide the sheet exactly stop fitting once the kerf is counted. A math problem usually ignores the blade. To get the textbook answer, set the kerf to 0.
How many pieces can I get out of a sheet of plywood?
It depends on the part size and the saw kerf: count how many fit along the sheet and how many across, allowing about 1/8 inch per cut, multiply, then try the part turned 90 degrees and keep the larger number. A layout that mixes both orientations sometimes fits more, which the calculator above checks for you.
Does this work for MDF, metal or glass?
Yes. The count depends only on the sizes, so any flat stock works: MDF, melamine, OSB, acrylic, sheet metal, glass, foam board or fabric. Set the kerf to match your cutting method: about 1/8 inch (3.2 mm) for a standard table saw blade, 3/32 inch (2.4 mm) for a thin-kerf blade, close to 0 for a laser or for glass that is scored and snapped.
Is the calculator free?
Yes. It is free, with no signup and no credit card. A free account is only needed to save projects in the full optimizer.