Standard Envelope Sizes In The UK (Measurements And Uses)
When someone asks “what size envelope for wedding invitations” the simplest answer is to start with the common UK envelope sizes and work back from your invite dimensions. In the UK we typically use C and DL sizes. Here are the practical sizes you’ll see from stationers, with their main uses:
- C6, 114 × 162 mm (4.5 × 6.4 in): The classic choice for A6 cards (105 × 148 mm). Great for single-sheet invites, RSVP cards, or enclosure cards. It’s the most common option for minimal suites.
- DL, 110 × 220 mm (4.3 × 8.7 in): Designed to hold an A4 sheet folded into thirds. We use DL when couples prefer a long, elegant envelope for a folded invitation or ceremony details.
- C5, 162 × 229 mm (6.4 × 9 in): Fits an A5 card (148 × 210 mm) comfortably. If your invitation is a folded A5 or you have several inserts, C5 gives extra breathing room.
- C4, 229 × 324 mm (9 × 12.7 in): Rare for wedding invites but useful if you’re sending an unfolded A4 programme, map or multiple large enclosures.
A couple of practical points: square invitations (for example 140 × 140 mm) don’t match the C-series proportions and usually require a slightly oversized envelope or a square envelope size. Square envelopes often need extra postage because they don’t run through postal sorting machines in the usual way.
We recommend picking an envelope that gives at least 3–5 mm clearance on all sides for easy insertion and to avoid edge wear in transit. If you’re including multiple inserts, err up a size rather than squeezing everything into the tightest fit.
Choosing The Right Size For Different Invitation Formats
Your invitation format is the primary driver of envelope choice. Below are common formats and the envelope we’d select for each:
- Single flat card (A6 or 105 × 148 mm): C6 envelope. It’s neat, affordable and looks proportionate. If the card has a thick stock or foiling, test-fit first.
- Folded A5 invitation (A5 when folded or a 210 × 148 mm folded): C5 envelope. We often suggest C5 when there’s an RSVP, details card and reply envelope, it keeps everything tidy without crowding.
- Long, tri-fold invitation (A4 folded into thirds): DL envelope. This offers a modern, streamlined look and slides nicely into a mailbox.
- Square invites: Use a square envelope sized 10–15 mm larger than the invitation. For example, a 140 × 140 mm invite works well inside a 155 × 155 mm envelope. Note: square envelopes usually incur higher postage and may need hand-sorting at the post office.
- Pocketfold or multi-piece suites: These often benefit from a bespoke or larger C5/C4 solution depending on thickness. If you have belly bands, vellum wraps or ribbon, account for the combined thickness rather than just the face dimensions.
Practical tip: measure the fully assembled invitation (including bands, wax seals and elk) and add at least 3–5 mm around the largest dimension. If the assembly is thicker than 3–4 mm, request a sample or ask your stationer for a mock-up to be sure it inserts cleanly.
Envelope Styles, Flaps And Materials That Affect Fit And Presentation
Envelope style isn’t just aesthetic, it changes how the invitation sits inside and how it’s perceived on arrival.
- Flap types: Pointed (V), straight (square), and wallet (side-opening) are common. Wallet and side-opening flaps can make inserting thick suites trickier: pointed flaps often provide a neater closure for single cards.
- Pocketfold envelopes: These have an internal pocket that keeps multiple pieces secure and present beautifully. They do add bulk and typically push you up a size, so plan for C5 even if your suite would technically fit a C6.
- Materials and liners: Laid, textured, metallic or handmade papers look luxurious but are usually thicker. Lined envelopes (printed or foil-lined) increase inside dimensions marginally and can interfere with automated sorting if the paper is heavy.
- Special finishes: Vellum wraps, belly bands, ribbons, wax seals and adhesive stickers all add thickness and complexity. Wax seals are charming but can crack in transit, consider a small glue dot to secure them and order a stronger envelope size to accommodate the extra bulk.
- Address windows and inner pockets: If you plan on using a windowed envelope for RSVP returns, ensure the window position aligns with each insert. For mailing, avoid transparent windows over sensitive personal info.
We recommend requesting envelope samples from your printer or stationer. Seeing and feeling a finished example will reveal whether a flap type or material is causing friction or bulging.
Addressing, Postage And Mailing Considerations
The right envelope size ties directly into postage and how smoothly envelopes pass through sorting.
- Postage basics: The more an envelope measures in size, thickness and weight, the higher the postage. Square envelopes and very thick suites often cost more because they can’t be machine-processed. The safest route is to weigh a finished, fully assembled invitation and get postage priced at a Post Office.
- Machine processing: Envelopes that are too rigid, oversized, or irregularly shaped can be rejected from automated processing. That means hand-sorting fees or higher rates. Using soft, flexible papers and keeping thickness consistent helps avoid that.
- Addressing and layout: Leave a clear address area (about 70–100 mm wide) on one side. If you use calligraphy or an address label, ensure it won’t obscure postage stamps or printed barcodes. Pre-printed postage (franking) may be possible for large runs but check with Royal Mail ahead of time.
- Return envelopes and RSVPs: If you include an RSVP envelope, pick a size that’s cheap to post back. A simple C6 for RSVP works well when your main invite is C5.
We always advise doing a test mail: send 5–10 sample invites to yourself and a few local guests. You’ll quickly see if anything jams, bends or arrives creased, and you’ll be grateful you caught it before the full run.
Ordering, Custom Sizes And Practical Checklist For Final Measurements
When it’s time to order envelopes, being methodical saves time and money. Here’s how we approach it:
- Order mock-ups early: Ask for a sample of your assembled invitation in the chosen envelope before full production.
- Consider custom sizes: If your design is non-standard, most printers will offer bespoke envelopes. Custom sizes can look exceptional but budget for slightly higher unit costs and more postage checks.
- Quantity and extras: Order 10–15% extra to cover addressing mistakes, testers, and keepsakes. If you’re hand-addressing, account for misinks.
- Practical final-measure checklist (use this at sign-off):
- External envelope width and height recorded in mm and inches
- Fully assembled invite width, height and maximum thickness
- Number and size of inserts listed (RSVP, details card, map)
- Will there be a belly-band, ribbon or wax seal? Note combined thickness
- Sample weighed and postage estimated at the Post Office
- Address placement and window alignment confirmed
- Quantity ordered + 10–15% extras requested
- Timing: Allow time for samples to arrive and for any corrections. We often advise adding an extra week into your stationery timeline for postage testing and potential reprints.
Conclusion
Answering “what size envelope for wedding invitations” starts with your invitation format and grows into considerations about presentation, postage and handling. Our practical approach is to measure the fully assembled suite, allow a small margin for ease, request a sample and test-mail several copies. When in doubt, choose the slightly larger C5/DL option rather than crowding a C6, it protects the design and reduces the risk of extra postage or damage. If you’re ready to order, weigh a finished sample at the Post Office and factor 10–15% extra envelopes for peace of mind. If you’d like, we can walk through your invite dimensions and recommend an exact envelope and postage strategy.
Key Takeaways
- When deciding what size envelope for wedding invitations, match the finished invite: C6 for A6 single cards, C5 for folded A5 or multi‑piece suites, and DL for A4 tri‑folds.
- Allow at least 3–5 mm clearance around the fully assembled invitation and size up for thicker elements like belly bands, vellum or wax seals to avoid insertion issues and edge wear.
- Use square envelopes 10–15 mm larger than a square invite (for example, a 140 × 140 mm card fits well in a 155 × 155 mm envelope) and budget for higher postage and possible hand‑sorting.
- Order envelope samples and run a test mail of 5–10 finished invites, then weigh them at the Post Office to confirm postage and machine‑processing suitability before full production.
- Request 10–15% extra envelopes and consider bespoke sizes only when necessary, as custom envelopes raise unit costs and can affect postage and sorting.
Frequently Asked Questions
What size envelope for wedding invitations should I choose?
When deciding what size envelope for wedding invitations, choose based on invite format: C6 (114×162 mm) for A6 flat cards, DL (110×220 mm) for A4 folded into thirds, and C5 (162×229 mm) for folded A5 or multi-piece suites. Allow 3–5 mm clearance and test-fit before ordering.
How much clearance should I leave when choosing the size envelope for wedding invitations?
When choosing the size envelope for wedding invitations, leave at least 3–5 mm clearance on every side so the invitation inserts easily and avoids edge wear. For thick stocks, liners or wraps, add extra room or opt for the next size and request a sample mock-up.
What size envelope for wedding invitations that are square?
For square wedding invitations, use a square envelope 10–15 mm larger than the invite (for example 140×140 mm fits well in 155×155 mm). Square envelopes often require higher postage and hand-sorting, so weigh a finished sample at the Post Office before ordering.
Are bespoke envelopes worth the extra cost for non-standard wedding invitations?
Bespoke envelopes give a perfect fit and unique finishes for non-standard shapes or luxury papers, but they typically cost more and may increase postage checks. They’re worthwhile for distinctive designs or thick suites; otherwise standard C-series sizes save money and simplify mailing.
Will wax seals, ribbons or heavy liners increase postage for wedding invitations?
Yes — wax seals, ribbons and heavy liners add thickness and rigidity, often making invites non-machinable and increasing postage. Secure decorative seals with a small glue dot, choose a slightly larger envelope and have a fully assembled sample weighed at the Post Office to confirm postage.