The standard Ethafoam STPE200 sheets sold by All Foam are 100cm × 120cm and 200cm × 120cm. If you need repeated rectangular pieces, planning how they fit on the parent sheet can help you estimate material use before requesting cut-to-size supply.
A simple layout can answer useful questions such as whether rotating the piece increases the quantity per sheet and whether the larger parent sheet reduces waste. It should still be treated as an estimate until the real cutting method and tolerance are confirmed.
Quick answer
For a first estimate, divide the parent-sheet length and width by the finished piece dimensions, round each result down to a whole number, then multiply the two counts. Repeat the calculation with the piece rotated. Use the better layout as a planning estimate, but allow for cutting method, tolerance and any required edge allowance before treating it as a production quantity.
Start with the two available parent sheets
The current All Foam STPE200 full-sheet sizes are:
- 100cm × 120cm
- 200cm × 120cm
The available thickness does not change the face dimensions of the sheet. A 25mm sheet and a 50mm sheet can have the same 100cm × 120cm footprint, but the material volume and finished part depth are different.
For yield planning, work with the length and width first. Then keep thickness, colour and quantity as separate parts of the specification.
A simple rectangular yield calculation
Suppose the finished piece is 50cm × 40cm and the parent sheet is 100cm × 120cm.
Along the 100cm side:
100 ÷ 50 = 2 whole pieces
Along the 120cm side:
120 ÷ 40 = 3 whole pieces
A simple grid therefore suggests:
2 × 3 = 6 pieces
Important: six pieces is a theoretical, zero-loss layout count. The dimensions fill the sheet exactly, so any cutting kerf, trimming or tolerance allowance could reduce the achievable finished quantity. Confirm the cutting method before quoting six pieces as a production yield.
This is useful for first-stage planning because the dimensions divide evenly on paper.
Now test the rotated layout:
100 ÷ 40 = 2 whole pieces
120 ÷ 50 = 2 whole pieces
That layout gives four pieces, so the first orientation is more efficient.
This is why rotation should always be checked.
Larger sheets do not always double the useful yield
The 200cm × 120cm sheet has twice the face area of the 100cm × 120cm sheet, but the number of finished parts does not automatically double for every dimension.
The piece dimensions determine how the rectangles nest within the available length and width.
For 50cm × 40cm pieces:
200 ÷ 50 = 4
120 ÷ 40 = 3
A simple, zero-loss grid suggests 12 pieces, exactly double the six-piece estimate from the smaller sheet. As with the six-piece example, this is not a guaranteed cutting yield because there is no spare space for cutting kerf, edge trimming or finished-size tolerances.
For a different rectangle, unused strips can change the result. The larger sheet may leave a proportionally different offcut.
Always calculate the actual dimensions rather than assuming the larger sheet gives a fixed multiplication factor.
Rotation can materially change the result
Consider a finished piece measuring 70cm × 50cm on the 100cm × 120cm sheet.
Layout one:
100 ÷ 70 = 1 whole piece
120 ÷ 50 = 2 whole pieces
Estimated yield: 2
Rotated layout:
100 ÷ 50 = 2 whole pieces
120 ÷ 70 = 1 whole piece
Estimated yield: also 2
In this example rotation does not improve the count.
Now consider a 60cm × 40cm piece.
Layout one:
100 ÷ 60 = 1
120 ÷ 40 = 3
Estimated yield: 3
Rotated:
100 ÷ 40 = 2
120 ÷ 60 = 2
Estimated yield: 4
The rotated layout is better.
A few seconds checking both orientations can make a meaningful difference when the quantity is repeated across many sheets.
The simple formula has limits
The grid calculation is intentionally basic.
It assumes:
- every piece is rectangular
- every piece has the same dimensions
- the pieces are laid in straight rows
- there is no extra edge allowance
- there is no cutting loss between parts
- no piece is rejected
Real conversion can require tolerance or process allowance. The exact cutting method can also affect how closely pieces can be nested.
For that reason, use the calculation to estimate material demand rather than as a guaranteed production yield.
If an exact commercial quantity depends on every sheet achieving a particular yield, confirm the cut plan before treating the estimate as final.
Mixed-size parts need a layout, not one formula
If one parent sheet needs to produce several different rectangles, the simple repeated-piece calculation is not enough.
For example, one sheet may need to produce:
- two base pads
- four side strips
- two top pads
Each component has a different length and width, so the most efficient arrangement may use the leftover area from one part to make another.
This is closer to a cutting-layout problem than a single yield calculation.
Sketch the parent sheet to scale and place the largest parts first. Then use the remaining areas for smaller pieces where practical.
For repeat commercial work, a consistent approved layout is more useful than recalculating the arrangement every time.
Offcuts are not automatically waste
A cutting layout can leave material that is too small for the main component but still useful for another job.
Ethafoam offcuts may be suitable for appropriate sample pads, test pieces, separators or future packaging development depending on their dimensions and condition.
If you control the cutting in-house, keeping useful offcuts can improve overall material use.
If All Foam supplies finished cut pieces, discuss the requirement based on the parts you actually need rather than assuming that every remaining area of a parent sheet can be converted into a saleable component.
Thickness changes volume, not the two-dimensional cutting count
A 50cm × 40cm rectangle occupies the same face area whether the foam is 10mm or 50mm thick.
The simple two-dimensional yield from the sheet is therefore the same.
However, thickness still affects:
- the amount of material in each finished part
- the suitability of the part for the packaging job
- handling and storage
- the overall depth of the finished packaging assembly
Do not choose a thickness simply because it gives the same number of pieces per sheet.
The Ethafoam thickness guide explains how to approach material depth separately.
White and grey use the same current sheet sizes
All Foam supplies STPE200 in white and grey using the same current 100cm × 120cm and 200cm × 120cm sheet formats.
Colour therefore does not change the basic rectangular yield calculation.
Choose colour from the product requirement or presentation preference, not because one colour appears to offer a different sheet area.
Check whether the part really is rectangular
A yield calculation based on length and width only works for rectangular pieces.
A converted insert with cavities, profiled edges or bonded sections requires a different production plan.
The outer rectangle may help estimate the maximum area occupied, but it does not describe the full conversion process.
If the requirement involves more than a straightforward rectangular cut, send All Foam the drawing or finished requirement so the conversion method can be reviewed.
Use the correct material family
Do not use an Ethafoam yield calculation as a substitute for material selection.
STPE200 is a semi-rigid, non-cross-linked expanded polyethylene packaging foam with a nominal density of 24 kg/m³.
The All Foam AFP30 and AFP45 closed cell range is different. Those are rigid cross-linked polyethylene sheets at 30 kg/m³ and 45 kg/m³.
If you are deciding between those materials, read the Ethafoam vs closed cell foam guide first. Once the material has been selected, then optimise the cut layout.
Example planning table
For quick planning, you can record each requirement like this:
- Parent sheet: 200cm × 120cm
- Material: STPE200
- Colour: grey
- Thickness: 25mm
- Finished piece: 50cm × 40cm
- Simple orientation A: 4 × 3 = 12 pieces
- Simple orientation B: 5 × 2 = 10 pieces
- Theoretical zero-allowance estimate: 12 pieces; confirm cutting method and allowances before calculating production quantities
This keeps the material specification and the yield assumption together.
When to choose cut-to-size supply instead
If you only need the finished pieces and do not want to manage the cutting layout yourself, use the Ethafoam cut-to-size service.
Send the finished dimensions, thickness, colour and quantity. For more detailed inserts, pads or separators, the Ethafoam cut-to-size packaging guide explains what additional information can help.
If you are deciding whether to buy the whole sheet or have the material prepared, see Ethafoam Cut to Size vs Full Sheets.
Plan yield before committing material
A simple sheet layout is one of the easiest ways to spot avoidable waste before cutting starts.
Use the two current STPE200 sheet sizes, test both orientations and keep thickness separate from the face-area calculation. For repeated or commercially important parts, confirm the real cutting allowance before relying on the theoretical maximum as the final production yield.
