What Size Envelope For Wedding Invitations?

Understanding Wedding Invitation And Envelope Sizes

Before we can decide what size envelope for wedding invitations is right, we need to unpack how sizes are actually measured and labelled.

How Invitations And Envelopes Are Measured

Wedding invitations and envelopes are almost always measured by their finished size:

• Invitations – measured by the size of the card once it’s fully trimmed (not including any decorative edges or deckled tearing).
• Envelopes – measured from the inside rectangle where the card sits, not including the flap.

This matters because our card needs a tiny bit of breathing room inside the envelope. If our invitation is, say, 127 x 178mm (a typical 5 x 7″ card in metric), we don’t choose an envelope that’s exactly that size. We go slightly larger so the card slides in smoothly without creasing.

As a rule of thumb, we want our envelope to be roughly 3–5mm larger than the card on each side.

UK Paper Sizes Versus US “5 x 7” Sizing

Here’s where it gets confusing. In the UK we’re used to A-sizes (A4, A5, A6 etc.), but wedding invitations are often described using US-style inches, especially “5 x 7”.

• A standard “5 x 7″ invitation” is 5 inches x 7 inches (approximately 127 x 178mm).
• UK stationery for weddings often still uses this size because it’s seen as classic and elegant.

By contrast, UK paper sizes look like this:

• A5 – 148 x 210mm
• A6 – 105 x 148mm

We don’t usually send an A5 sheet on its own as a wedding invitation: instead, we might design a 5 x 7″ card, or something close, then pick a coordinating envelope size. So when we see US-style sizing on wedding blogs or Pinterest, we just need to match it to a realistic UK envelope measurement in millimetres.

Allowing Enough Wiggle Room For Your Suite

Most wedding invitations aren’t just a single card. We often have:

• Main invitation card
• Details / information card
• RSVP card
• Perhaps a map, accommodation note, or small itinerary

All of this adds bulk and thickness. If we choose an envelope that only just fits one card, the entire suite will look stuffed and may even buckle.

We want to allow:

• A little horizontal and vertical room for multiple pieces
• Enough depth that the stack still lies flat

A good approach is to design or confirm our full suite first, stack the cards neatly, and then choose an envelope that feels comfortable around it, not loose, but definitely not tight.

Standard Envelope Sizes For Wedding Invitations

Standard Envelope Sizes For Wedding Invitations

Let’s look at the envelope sizes we’re most likely to use for wedding invitations in the UK, and what they work best with.

Most Popular Size: Envelopes For 5 x 7 Invitations

A 5 x 7″ invitation (about 127 x 178mm) is the modern classic. It feels substantial in the hand and gives enough space for elegant typography.

For this size, we typically use an envelope that’s around:

• 130 x 184mm or 133 x 184mm (often sold as “5 x 7 envelopes” in the UK)

This gives that vital few millimetres of breathing room on each side. In US terms, you may see this called an A7 envelope, but in the UK it’s usually just labelled “5 x 7 envelope” with the metric conversion on the pack.

If our main question is what size envelope for wedding invitations that are 5 x 7?, this is the answer: anything in the 130–135mm x 184–190mm range is perfect.

Other Common Rectangular Envelope Sizes (C6, DL, C5)

If we’re not using 5 x 7, or we’re mixing formats for our inserts, these standard envelope sizes are helpful:

• C6 envelope – 114 x 162mm
• Best for A6 cards (105 x 148mm)
• Great for RSVP cards or simple, smaller invitations
• DL envelope – 110 x 220mm
• Fits a third of A4 (compliment slip size)
• Works for slim, modern-style invitations or folded cards
• C5 envelope – 162 x 229mm
• Fits an A5 card (148 x 210mm)
• Ideal if we want a slightly larger-than-average invitation or we’re enclosing a folded A4 information sheet

These sizes are widely available in the UK in everything from luxury cotton stocks to simple white envelopes, which can help us keep costs and lead times reasonable.

Square Envelopes And When To Use Them

Square envelopes have a very “wedding” feel, perfect for modern, minimal, or luxury designs. Popular sizes include:

• 155 x 155mm (often used with 148 x 148mm cards)
• 170 x 170mm (for slightly larger square invitations)

We might choose square envelopes when:

• Our invitation design is a square card instead of rectangle
• We want a bold, contemporary look
• We’re using a vellum wrap or ribbon that suits a squarer shape

But, square envelopes can mean higher postage with Royal Mail (they often fall into Large Letter), so we’ll weigh that up in the postage section.

Small Envelopes For RSVP And Detail Cards

Smaller envelopes are typically used for RSVP cards and occasionally mini information cards.

Common sizes include:

• C7 – 81 x 114mm (for A7 cards)
• Mini 90 x 145mm / 95 x 145mm style envelopes

When choosing:

• Make sure our RSVP card is around 5–8mm smaller than the envelope in both directions
• Consider how the small envelope will sit inside the main invitation envelope, we don’t want something so bulky it distorts the outer envelope

Most of us will end up with a combination such as:

• 5 x 7″ main invitation in a 130 x 184mm outer envelope, and
• A6 or A7 RSVP card in a C7 or C6 envelope, tucked inside.

How To Choose The Right Envelope Size For Your Wedding

How To Choose The Right Envelope Size For Your Wedding

Now we know the common sizes, how do we decide which one is right for our wedding specifically?

Start With Your Invitation Size And Layout

The most reliable way to answer what size envelope for wedding invitations is to start with the invite, not the envelope.

Ask ourselves:

• Is our main card 5 x 7″, A6, A5, or square?
• Is it portrait or landscape?
• Are we using one card or a more layered design?

Once the invitation size is fixed, we can pick an envelope that’s roughly 3–5mm larger on each side.

Example:

• Main card: 127 x 178mm (5 x 7″)
• Ideal envelope: around 130–135 x 184–190mm

If we’re having our invitations printed by a stationer, it’s worth asking: “Which envelope size do you recommend for this design?” Good studios will already know the best match.

Accounting For Multiple Inserts And Thickness

Thickness catches a lot of couples out. A single card may fit perfectly in a snug envelope, but add:

• An RSVP card and envelope
• An information card
• A wax seal, belly band or ribbon

…and suddenly the whole stack is straining at the seams.

To avoid this, we can:

1. Stack our full suite as it will be sent.
2. Measure it (or simply test it) inside the intended envelope.
3. If the flap struggles to lie flat, size up slightly or streamline the inserts.

For very elaborate suites (thick card stocks, multiple layers, pockets, or ribbon ties), it can be worth jumping from a 130 x 184mm envelope to something a touch larger, as long as we stay within our target Royal Mail band.

Inner And Outer Envelopes, Pockets, And Wraps

Traditional wedding etiquette sometimes uses inner and outer envelopes:

• Inner envelope – unsealed, often printed with guests’ names only, protecting the suite
• Outer envelope – sealed and addressed for posting

If we’re going down this route, we’ll need to make sure:

• The inner envelope comfortably fits the invitation suite
• The outer envelope then fits the whole bundle plus the inner envelope

Likewise with pocketfolds, vellum wraps, or belly bands:

• Design or choose the pocket/wrap first
• Confirm the final “closed” size (once everything’s folded or assembled)
• Then choose an envelope that’s slightly bigger than that size, not just the card alone

Matching Envelope Size To Your Wedding Style And Budget

Envelope size isn’t only practical: it also affects the look and cost of our invitations.

Style-wise:

• 5 x 7″ envelopes feel classic and slightly luxurious
• C6 / A6 formats feel a touch more informal and compact
• Square envelopes read as contemporary, bold, and design-led

Budget-wise:

• Smaller, standard sizes like C6, DL, and C5 are often cheaper and easier to source in a wide range of colours.
• Larger or non-standard sizes, or very thick card, can push postage into Large Letter.

If we’re working to a tight budget, we might choose a standard rectangular size that posts as a normal Letter, then invest in nicer paper, printing, or an envelope liner instead of sizing up.

Postage And Mailing Considerations In The UK

Postage And Mailing Considerations In The UK

Choosing what size envelope for wedding invitations isn’t just about fit: it’s also about how much Royal Mail will charge us.

Royal Mail Size Bands: Letter Versus Large Letter

In the UK, wedding invitations usually fall into either Letter or Large Letter bands.

As of recent Royal Mail guidelines (always check before posting):

• Letter (Standard Letter)
• Max size: 240mm x 165mm x 5mm
• Max weight: 100g
• Large Letter
• Max size: 353mm x 250mm x 25mm
• Max weight: 750g

Most 5 x 7″ invitation envelopes around 130 x 184mm technically fall within Large Letter height but are under Letter width. But, once we add thickness and card weight, many wedding invitations tip into Large Letter pricing anyway.

The safest approach is to:

• Assume a Layered or bulky suite will likely be Large Letter
• Keep very minimal, one- or two-card suites thinner if we’re aiming for Letter pricing

How Square And Oversized Envelopes Affect Postage

Square and oversized envelopes tend to push postage up:

• Square envelopes are often treated less like a standard Letter and more like Large Letter, even when small.
• Larger formats such as C5 or 170 x 170mm almost always sit in the Large Letter category once stuffed with card.

So if we’re torn between classic 5 x 7″ rectangles and big square envelopes, it’s worth doing a quick cost comparison for, say, 80–120 invitations. That small difference per piece adds up.

Weighing, Testing, And Avoiding Mailing Surprises

To avoid any unpleasant post office moments right before sending:

1. Assemble one full invitation suite with all inserts, seals, ribbons, etc.
2. Place it into the chosen envelope.
3. Take this fully assembled sample to the post office and ask them to measure and weigh it.

They’ll confirm whether:

• It’s Letter or Large Letter
• How much postage per invite we need

We can then buy the correct stamps (often online) and apply them at home, confident that everything will go through the system smoothly.

It’s also sensible to post a test invitation to ourselves, especially if we’re using:

• Dark envelopes
• Wax seals
• Unusual sizes or very thick card

This lets us check how the envelope travels, whether barcodes or labels obscure the design, and if the contents arrive pristine.

Practical Design Tips For Wedding Invitation Envelopes

Practical Design Tips For Wedding Invitation Envelopes

Once we’ve nailed what size envelope for wedding invitations is right, we can focus on making them look beautiful and function smoothly.

Choosing Colours, Liners, And Finishes

Envelopes are often the first glimpse of our wedding style, so it’s worth giving them attention.

We can consider:

• Colours – Soft neutrals (ivory, nude, dove grey) feel classic: rich tones (forest, burgundy, navy) feel luxurious: pastels (sage, blush, powder blue) are perfect for romantic themes.
• Envelope liners – Printed or coloured liners instantly elevate a simple envelope and can tie in with our invitation artwork.
• Finishes – Textured, cotton, or handmade-style envelopes give a tactile, artisanal feel: smooth envelopes feel more modern and minimal.

Just remember that darker shades may need white ink printing, metallic pens, or address labels so the addresses are clearly legible for postal scanners.

Addressing, Calligraphy, And Printing Options

We have a few options for addressing:

• Handwritten addressing – Personal and charming, but time-consuming: our handwriting needs to be clear and bold.
• Modern calligraphy – Beautiful for a luxury feel. We can hire a calligrapher or use calligraphy-inspired fonts printed directly onto the envelopes.
• Digital printing or labels – Clean, consistent and practical, especially for large guest lists.

If we’re printing directly onto envelopes, we should:

• Double-check our envelope size matches the printer’s capability
• Order a few extra envelopes for test runs

We may also want to print a small return address on the flap, particularly if we’re sending some invitations overseas.

Ordering Samples And Allowing For Spares

Before we commit to a full order, it’s wise to:

• Order a sample of our chosen envelope size and colour
• Test it with a printed invitation card to ensure the fit feels right

When it comes to final quantities, we should always allow for:

• At least 10–15% extra envelopes to cover addressing mistakes, last-minute guest list changes, and test prints
• A couple of fully assembled suites to keep as keepsakes or for our photographer on the day

It’s surprisingly easy to miswrite an address or smudge ink, so those spare envelopes almost always get used.

Conclusion

Conclusion

Choosing what size envelope for wedding invitations comes down to a simple sequence: decide the invitation size and layout, allow a few millimetres of wiggle room around the full suite, then check the Royal Mail size and weight before committing.

For most of us in the UK, a 5 x 7″ invitation in a 130–135 x 184–190mm envelope is the ideal sweet spot: elegant, practical, and familiar to printers and stationers alike. From there, we can play with colours, liners, and finishes to create something that feels completely ours, without any last-minute postage dramas.

If we treat envelopes as part of the design, not an afterthought, the moment our guests open the post will feel every bit as special as the invitation inside.

Frequently Asked Questions

What size envelope for wedding invitations is best for a 5 x 7″ card?

For a standard 5 x 7″ wedding invitation (about 127 x 178mm), choose an envelope around 130–135 x 184–190mm. In the UK these are usually sold as “5 x 7 envelopes”. This gives 3–5mm wiggle room so the suite slides in neatly without creasing.

How much bigger should the envelope be than the invitation?

As a rule of thumb, your envelope should be roughly 3–5mm larger than the finished invitation card on each side. This extra space allows for easy insertion, prevents corners from catching, and gives room for multiple inserts such as RSVP and information cards without the envelope looking overstuffed.

Which envelope size should I use instead of 5 x 7 for UK wedding invitations?

If you’re not using a 5 x 7″ card, common UK options are C6 (114 x 162mm) for A6 invitations, DL (110 x 220mm) for slim or folded designs, and C5 (162 x 229mm) for A5 cards or folded A4 sheets. All are widely available in many colours and finishes.

Do square wedding invitation envelopes cost more to post in the UK?

Square envelopes often fall into Royal Mail’s Large Letter band once filled, so they typically cost more to post than standard rectangular envelopes. Popular wedding sizes like 155 x 155mm or 170 x 170mm look very modern, but you should factor in higher postage when budgeting for 80–120 invitations.

How do I check if my wedding invitation envelope is Letter or Large Letter with Royal Mail?

Assemble one full invitation suite, including all inserts, ribbons and seals, place it in your chosen envelope, then take this sample to the Post Office. They’ll measure thickness, size and weight, confirm if it’s Letter or Large Letter, and tell you the exact postage you’ll need per envelope.

Can I use handmade paper invitations with standard wedding invitation envelopes?

Yes, but handmade or deckle-edge cards are usually thicker and slightly irregular, so choosing the right size envelope for wedding invitations is crucial. Go towards the larger end of the recommended range and test a fully stacked suite in a sample envelope to ensure the flap closes comfortably without bending the edges.