A4 and US Letter label sheets are never interchangeable, even when the individual label looks the same size. The sheets are different dimensions (A4 is 210 × 297 mm; Letter is 8.5 × 11″), so the margins and row counts differ. In our database, A4 and Letter geometries are always assigned separate Layout Family IDs, 38 A4 families and 97 US Letter families, by rule.
Firms that work across US and European or international matters hit this constantly. A template that prints perfectly on your US Letter labels will not line up on the A4 equivalent, because the taller, narrower A4 sheet redistributes the same labels differently.
A caveat about A4 data
A number of A4 layouts in the corpus arrived with unreported margins. Rather than guess, we flag those for closed-form back-computation from the 210 × 297 mm sheet before we publish full geometry. So some A4 pages show verified label dimensions but a note that margins are being finalized. That honesty is deliberate.
Working across both
- Keep two template sets, one A4 and one Letter, and never cross them.
- Confirm the sheet size first. It is the fastest way to rule out half the catalog.
- For A4 families flagged "back-compute," verify margins against the vendor before a large run.