Royal Mail Size & Weight Limits — What Counts as a Letter, Large Letter, or Parcel?

Royal Mail pricing is based on a combination of the item's format (letter, large letter, small parcel, medium parcel) and its weight. Getting this wrong at the online checkout is one of the most common reasons parcels arrive with a surcharge sticker — meaning the recipient has to pay extra to collect it. We check and weigh everything at the counter so this doesn't happen to you.

Letter - Max size: 240mm × 165mm × 5mm - Max weight: 100g - Cheapest format — ideal for cards, flat documents, folded letters

Large Letter - Max size: 353mm × 250mm × 25mm - Max weight: 750g - Suitable for padded envelopes, small booklets, A4 documents

Small Parcel - Max size: 450mm × 350mm × 160mm - Max weight: 2kg - Covers most standard boxes and packets

Medium Parcel - Max size: 610mm × 460mm × 460mm - Max weight: 20kg - Suitable for larger boxes and bulkier items

Measure the longest side, the second longest side, and the depth. If your item is at all soft or compressible, measure it lightly pressed flat — not squeezed. The size bands are checked at the sorting office, not just on the scales.

If postage is underpaid, Royal Mail will attempt delivery but leave a "something for you" card. The recipient must pay the underpaid amount plus a £1.50 handling fee before it can be released.

We avoid this entirely by weighing and measuring at the counter before posting. There's no extra charge for this — it's just what we do.

• Greeting cards in thick padded envelopes often exceed the letter depth (5mm) and should be posted as large letters
• Books or catalogues frequently exceed 750g and therefore need small parcel pricing
• Rolled-up posters in postal tubes must be measured along their longest dimension

Just bring your item to any of our branches and we'll measure, weigh, and confirm the correct format and price on the spot. Visit our [branches page](/branches) for opening hours.