Physical mail reference
How large can a regular letter be?
A side-by-side reference for ordinary domestic letters. Carrier categories differ, so this does not compare prices or guarantee that a format qualifies for an equivalent service abroad.
Quick answer: C4 (324 × 229 mm) fits within the stated domestic letter maximums shown for PostNL and La Poste, but not Royal Mail’s standard “Letter” category. Thickness and weight can move an item into another category.
| Postal operator | Minimum | Ordinary-letter maximum | Maximum thickness | Maximum weight | Useful category distinction |
|---|---|---|---|---|---|
| PostNL (Netherlands) | 140 × 90 mm | 380 × 265 mm | 32 mm | 2 kg | Small: max 229 × 162 × 5 mm; Large: max 324 × 229 × 10 mm |
| Royal Mail (UK) — Letter | Not stated on checked category page | 240 × 165 mm | 5 mm | 100 g | “Large Letter” is a separate category; check it before using C4 |
| La Poste (France) | 140 × 90 mm | Length + width + thickness max 100 cm; longest side max 60 cm | 30 mm | 2 kg | Limits shown for metropolitan France, Andorra and Monaco |
| Deutsche Post (Germany) — Standardbrief | 140 × 90 mm | 235 × 125 mm | 5 mm | 20 g | Compact, Groß and Maxi letters have separate dimensions and weights |
Common envelope reference
DL: 220 × 110 mm. C5: 229 × 162 mm. C4: 324 × 229 mm. These are envelope standards, not postal service classes; compare their dimensions with the carrier row and then recheck the current service page.
Before posting
- Measure the sealed item, including its thickest point.
- Check the destination-specific service if posting abroad.
- Confirm the category and current postage with the operator.