Size is specified from the contents, not from a chart
There is no universal pouch size chart, and a supplier publishing one is describing their own existing patterns rather than your product. The internal dimensions come from the packed contents plus the clearance the closure needs.
This is the single most common reason a first sample fails: the buyer sent a size they had in mind, the factory made it accurately, and the product does not fit or the pouch will not close.
Measure the packed object, not the object
Measure what actually goes in, in the state it goes in. A boxed item is measured boxed. A device stays in its case. A jewelry set is measured as a set, not as its largest piece.
Record three dimensions — width, height and depth or thickness — and the weight. Depth is the one most often omitted and it is what determines whether a flat pouch works or a gusset is needed.
For irregular shapes, measure the largest dimension in each axis, then note where the bulk sits. A pouch for a tall narrow bottle behaves differently from one for a wide flat compact of the same volume.
Clearance the closure needs
The internal size is not the packed size. Different closures consume different amounts of length and width:
Drawstring needs headroom above the contents for the channel and for the gather. A pouch sized flush to the product will not close cleanly.
Envelope flap needs flap depth beyond the contents, and the flap has to lie flat when the pouch is full, not just when empty.
Zip needs seam allowance on all sides and a straight run for the zip tape.
Fold-over needs enough length to fold and still cover.
Rather than guessing these, state the packed dimensions and the closure you want, and let the pattern be worked out from both.
Flat, gusseted or shaped
Decide early whether the pouch lies flat or stands up. A gusset is a different pattern, not a bigger version of a flat pouch, and switching after sampling means re-sampling.
Flat suits thin, single items — a card, a document, a flat pouch of jewelry. Gusseted suits sets, bottles, and anything with real depth. Shaped or structured suits presentation pieces where the pouch should hold its form empty.
What to send with the inquiry
A complete sizing brief contains: packed dimensions in all three axes, weight, the closure you want, whether it should lie flat or stand, and — where it matters — a photo of the product beside a ruler.
If one pouch has to cover several product variants, send the largest and smallest so the internal size can be set against both rather than against an average.
Then approve the physical sample packed. An empty pouch tells you almost nothing about fit, closure behaviour or how it presents at the counter.