What Fits Through a Letterbox: A UK Guide

We make cards, pin badges and prints in the UK, all of them flat enough to post. We don't sell flowers, so the guide below is a straight guide - the cards and prints at the end are the only things we're selling.

The point of a letterbox gift is that nobody has to be in. Get the thickness wrong and it becomes a parcel, a card through the door and a trip to the depot - the opposite of a kind gesture.

Here's what actually goes through, and how UK postage sizes work. Check current Royal Mail sizes and prices before you post, as they change.

The size that matters is thickness

• UK letterbox openings are typically around 25cm wide and quite shallow, so depth is what catches people out, not width.
• Royal Mail's large letter format allows roughly 2.5cm of thickness - that's the threshold most letterbox gifts are designed around.
• Anything thicker is priced and handled as a parcel, and may not fit the door at all.
• Rigid packaging counts in full. A 2cm gift in a 1.5cm box is a parcel.
• New builds and flats often have narrower slots or a communal box, so send thinner than the limit if you're unsure.

What goes through easily

• Cards and postcards, obviously, including with a small flat gift tucked inside.
• Unframed prints, posted flat between board rather than rolled in a tube - tubes are parcels.
• Pin badges, keyrings and bookmarks.
• Tea bags, coffee sachets and flat chocolate bars in a slim box.
• Seed packets, stickers and photographs.
• Gift cards and vouchers, inside a card.

What doesn't

• Mugs, candles and anything in a jar.
• Rolled posters in tubes.
• Framed prints - the glass is the problem before the depth is.
• Bouquets sold as letterbox flowers still arrive as a fairly deep box; many won't fit older slots.
• Anything you'd be upset about if it was left on a doorstep.

Posting so it arrives right

• Write the postcode clearly and in the right place - it's the bit machines read.
• First class for anything timed to a date; second class is fine for a card sent simply because.
• For sympathy and get well post, send on a Monday or Tuesday so it doesn't sit over a weekend.
• Use a stiffened envelope for prints and write "do not bend" - it helps more than people think.
• Put your return address on the back in case the address is out of date.

Shop thinking of you cards

Prints that post flat

A5, A4 and A3 art prints, drawn in house and printed in the UK.

How to write it so it lands

• Thickness, not width, is the problem.
• Post prints flat, never in a tube.
• Send early in the week for get well and sympathy post.

Where to shop next

• Letterbox gifts instead of flowers
• Letterbox sympathy gifts
• Thinking of you gifts by post
• Letterbox gifts for someone far away
• The rise of letterbox flowers
• What to write in a sympathy card
• Thinking of you messages
• Wall art and prints
• All guides
• Planning the party? Birthday party ideas
• How to make a balloon arch
• Photo booth prop ideas
• Pin badges

Frequently asked questions

What size fits through a UK letterbox?

Thickness is the limiting factor. Royal Mail's large letter format allows around 2.5cm deep, and most UK letterboxes are built around that. Check current Royal Mail sizes before posting.

Do letterbox gifts always fit?

Not always. Older doors, narrow slots in new builds and communal boxes in flats can all be tighter than the standard, so send something thinner than the limit if you're unsure.

Can you post a print through a letterbox?

Yes, if it's unframed and sent flat between stiff board. Rolled tubes are parcels and won't go through the door.