What this calculator solves
Use Poly Mailer Size to estimate usable internal width and length around a flexible or already protected product. Thickness consumes both face dimensions, so flat product length and width alone are insufficient. This tool is not a box-sizing calculation and provides no crush protection assessment.
How to choose the inputs
Measure the packed item in the orientation used for insertion. Enter maximum thickness without compressing the product, usable insertion clearance, and the flap space that must remain above the item. Compare the result with the supplier’s usable dimensions below the adhesive line, not only the nominal cut size.
| Input | How to prepare it |
|---|---|
| Product length | Measure product length on the finished item or container surface named here; keep it in the selected unit and include normal production variation. |
| Product width | Measure product width on the finished item or container surface named here; keep it in the selected unit and include normal production variation. |
| Product thickness | Measure product thickness on the finished item or container surface named here; keep it in the selected unit and include normal production variation. |
| Insertion clearance | Measure insertion clearance on the finished item or container surface named here; keep it in the selected unit and include normal production variation. |
| Seal flap allowance | Measure seal flap allowance on the finished item or container surface named here; keep it in the selected unit and include normal production variation. |
How the calculation works
- Validate the Poly Mailer Size Calculator manifest: confirm that product length, product width, product thickness describe the same Poly Mailer Size Calculator pack, batch, or planning period.
- Calculate mailer size: apply Mailer width = product width + thickness + 2 × clearance; mailer length = product length + thickness + clearance + flap without rounding intermediate values for Poly Mailer Size Calculator.
- Review the mailer size breakdown: use the primary result for the stated decision and the secondary values to identify the input or constraint driving this Poly Mailer Size Calculator result.
Worked example
A 10 × 8 × 2 in item with 0.5 in clearance and a 2 in flap needs about 11 × 14.5 in of usable internal mailer space.
Next action: After: perform an insertion and seal trial, then compare finished external dimensions.
How to interpret the result
Round up to a stocked mailer and test insertion, seal engagement, corner stress, and label surface. If the recommendation jumps to a much larger size, consider rotating the item or using a gusseted format. A tight result needs allowance for seams and manufacturing tolerance.
Common mistakes
- Using outside nominal mailer dimensions as usable space.
- Ignoring product thickness or rigid corners.
- Counting the adhesive flap as product cavity.
- Compressing a soft item without checking rebound and seal load.
Assumptions and limitations
The model assumes a regular flexible enclosure and simple thickness allowance. It excludes gusset geometry, seam width, stiffness, sharp edges, compression limits, closure strength, tamper requirements, and carrier acceptance.
Related workflow
- Before: decide whether the item is suitable for a flexible container.
- After: perform an insertion and seal trial, then compare finished external dimensions.