Compare coffee bag thickness only after confirming the unit, whether the figure describes one wall, and whether it refers to the complete laminate. A quotation saying “4 mil” cannot be compared directly with one saying “100 microns” until those definitions match. Thickness is a specification to check, not a shortcut for choosing the best bag.
For a roaster ordering from more than one supplier, this small clarification can prevent a sample approved under one interpretation from being ordered under another.
Microns and mils are different units
A micron is a micrometre, written as µm. A mil is one-thousandth of an inch; it is not a millimetre. NIST Handbook 133, 2026, Appendix E gives the exact conversion: 1 mil = 0.001 inch = 0.0254 millimetre = 25.4 micrometres.
Use micrometres = mils × 25.4. To convert in the other direction, divide micrometres by 25.4.
| Thickness in mils | Equivalent in micrometres | Equivalent in millimetres |
|---|---|---|
| 2 mil | 50.8 µm | 0.0508 mm |
| 3 mil | 76.2 µm | 0.0762 mm |
| 4 mil | 101.6 µm | 0.1016 mm |
| 5 mil | 127.0 µm | 0.1270 mm |
These are calculated unit equivalents, not HEYI product specifications or recommended coffee bag thicknesses. For example, 100 µm is approximately 3.94 mil. Whether it is acceptable against a nominal 4-mil specification depends on the agreed tolerance and measurement basis.
Ask whether the number describes one wall
Have the supplier state “single-wall thickness of the finished laminate” if that is what the purchasing specification requires. A measurement taken through both faces of a flattened bag answers a different question.
As a simplified arithmetic example, two flat walls measuring 100 µm each add up to 200 µm. That does not make either wall a 200-µm laminate. Avoid treating measurements across a zipper, seal or folded gusset as interchangeable with a flat-panel reading. Specify where the measurement should be taken and ask the supplier how its reported figure was obtained.
Separate overall thickness from the layer description
A total thickness number does not tell you what every layer is made from. Ask for the proposed material structure alongside the overall nominal thickness. If the quotation lists individual layer thicknesses, clarify how the finished laminate total is defined and whether coatings or adhesives are included.
Do not assume two equal-thickness bags have equivalent protection or processing behaviour. Request evidence for the performance your project needs separately, rather than asking a thickness figure to stand in for a complete material specification.
Our coffee packaging buyer’s guide discusses material and bag-format choices more broadly. This thickness check belongs alongside that selection process.
Agree the measurement method and tolerance
ISO 4593:1993 addresses thickness measurement of plastic film and sheeting by mechanical scanning. ISO lists it as confirmed in 2025; its public abstract excludes embossed film and sheeting. A buyer should therefore ask whether the proposed method fits the actual material and surface, rather than requesting a standard number without checking its scope.
Nominal thickness and measured results should be labelled separately. Ask how many measurements are taken, where samples come from and how variation is reported. Agree the acceptance tolerance in writing before placing the order. This article does not prescribe a universal tolerance or claim that HEYI has tested a particular structure to this method.
A compact thickness specification for your purchase order
- Unit: state µm or mil explicitly.
- Basis: identify one wall or another agreed measurement basis.
- Construction: name the approved laminate specification and revision.
- Target: distinguish nominal thickness from acceptance limits.
- Inspection: agree method, sample locations and reporting format.
- Changes: require review before substituting a different structure.
Frequently asked questions
Is 4 mil the same as 4 mm?
No. Four mil equals 0.1016 mm. Write the full unit on the quotation and approval sheet to avoid an expensive misunderstanding.
Can I choose a coffee pouch by thickness alone?
No. Confirm the proposed structure and relevant performance requirements as well as the thickness. There is no single thickness recommendation in this guide for every coffee product or filling process.
What if a sample reading differs from the quote?
First check units, single-wall versus combined-wall measurement, location and method. Then compare the result with the agreed tolerance. Keep the sample and report identifiable while the supplier investigates.
Confirm the specification before approving artwork
Review HEYI’s custom coffee packaging pouches, then send your coffee bag requirements with the preferred format and any existing thickness specification. Ask for the material structure and measurement basis to be written into the quotation so your team can review the same bag specification throughout the project.
References checked November 9, 2026: NIST Handbook 133 (2026), Appendix E, and ISO 4593:1993 public abstract and status, linked above. Conversion examples are calculations, not product test results.