First published: 9 April 2018 | Updated: 3 September 2026

A mail-ready postcard needs to get three things right: it has to fit Royal Mail’s size and weight rules for the postage you’re paying for, the back needs a clear layout for the address and message, and the artwork needs proper bleed so nothing gets cut off in the trim. Get those right and everything else, from paper choice to your message, is about making it as effective as possible. Here’s how to set one up properly, whether you’re sending a personal note or a marketing mailer.

Quick answer at a glance:

Postcard size	Royal Mail category	Approx. postage (2026)
Up to 240mm x 165mm x 5mm, under 100g	Letter	£1.80 (1st class) / 91p (2nd class)
Larger than 240mm x 165mm, up to 353mm x 250mm x 25mm, under 750g	Large Letter	£3.30 (1st class) / £1.55 (2nd class)

Worth knowing: a standard A6 postcard (105mm x 148mm) comfortably fits the Letter rate, but an A5 postcard (148mm x 210mm) exceeds the 165mm width limit and gets charged at the pricier Large Letter rate instead. If postage costs matter for your mailing, A6 is the safer size.

UK Postcard Size and Postage Rules

Royal Mail classifies mail by size, weight, and thickness, not just by whether something is technically “a postcard.” To qualify for the cheaper Letter rate, your postcard needs to be:

• No larger than 240mm x 165mm
• No thicker than 5mm
• No heavier than 100g.

Anything bigger than this, including many A5-sized postcard templates, gets bumped up to the Large Letter rate instead; still perfectly postable, just at a higher price. Royal Mail’s rates and size bands do change from time to time, so it’s worth double-checking the current rates on royalmail.com before a large mailing run, particularly for business use, where the difference adds up with volume.

Sending Postcards Internationally

If you’re posting outside the UK, standard UK postage doesn’t apply; you’ll need an international stamp or service, and rates vary by destination zone. It’s worth checking Royal Mail’s current international pricing before sending, since rates and zone groupings are updated periodically. Some destination countries also have their own postcard size or thickness conventions worth being aware of if you’re sending anything non-standard (heavily embellished, oversized, or unusually thick).

Ready to put this into practice? Browse our postcard templates or upload your own design to get started.

 

Setting up Your Postcard for Print (Bleed and Safe Zone)

If your design runs right to the edge of the card (a full-bleed photo or background colour), you need to build in bleed so nothing prints with an unwanted white border after trimming.

• Bleed: extend your background or image 3mm beyond the edge of your final postcard size on all sides. This gives the trim a small margin for error.
• Safe zone: keep any text or important design elements at least 4-5mm inside the trim line, so nothing risks being cut off.
• Easiest approach: download the official postcard artwork template for your chosen size before you start designing. It already has the bleed and safe zone marked out, so you don’t have to measure manually. For more details on how bleed works, see our full guide to bleed printing.

Designing the Front

The front of your postcard is the part that gets noticed first, so it carries the most weight, whether that’s a personal photo or a marketing message.

For personal postcards: a single strong photo or image usually works better than a cluttered design. Keep any text minimal, save your message for the back.

For business or marketing postcards: lead with one clear focal point (a product photo, an offer, or a bold headline) rather than trying to fit everything on. Include your logo, but keep it modest; this is a mailer, not a business card. If there’s a call to action (“Scan to redeem,” “Visit us this weekend”), make it the most visually prominent piece of text after the headline.

Print-Ready Artwork: Resolution and Colour Mode

To make sure your postcard prints as sharp as it looks on screen:

• Set your artwork to 300 dpi (dots per inch) for the final print size. Anything lower can look soft or pixelated once printed, even if it looks fine on a screen.
• Design in CMYK, not RGB. Screens display colour in RGB, but printing uses CMYK; converting late (or not at all) can shift your colours, especially blues, greens, and bright oranges, once printed.
• If you’re using a photo, check that it’s a high-resolution original rather than one pulled from a website or social media; web images are almost always too low-resolution for print.

 

Got the perfect photo picked out? Upload it and we’ll turn it into a postcard on sturdy 350gsm card, ready to post.

 

Setting up the Back: Message, Address, and Stamp

 

The back of a postcard conventionally splits into two halves:

• Right half: the recipient’s address, with the stamp in the top-right corner.
• Left half: your message (or, for a marketing postcard, a shorter promotional message alongside your business details).

Keep the address side genuinely clear of decoration or heavy design elements; this isn’t just about looking tidy. An address that’s hard to read risks delays. If you’re printing your own address labels or using a pre-printed layout, leave enough space on the right for a full name, address, and postcode without cramming.

Choosing Your Paper and Finish

At Banana Print, our postcard printing is done on 350gsm card, sturdy enough to survive the post without needing a sealant or extra reinforcement, in your choice of silk board or an eco-friendly recycled board, with a matte or gloss finish. For a comparison of what different paper weights and finishes suit different jobs, see our guide to paper types for printing and what GSM actually means.

 

Not sure whether silk or recycled suits your brand better? See both finishes side by side before you order. 

 

Writing an Effective Message

Postcards work because the space is short, so make every word count.

• Personal postcards: write your message on the left side, keep it warm and specific rather than generic, and remember it’s technically visible to anyone handling the card in transit, so keep anything private off it.
• Marketing postcards: lead with the benefit to the reader, not your business name. Keep the message to one or two short sentences plus a single, clear call to action. A postcard with three competing messages usually converts worse than one with a single, obvious next step.

Common Mistakes to Avoid

• Exceeding the size or weight limit without realising it. Adding thick embellishments, heavy card stock, or attachments can tip a postcard from Letter rate into the pricier Large Letter category, or make it unpostable altogether if it exceeds Large Letter limits.
• Cramming the address side. A busy design behind the address text makes it harder to read and increases the risk of delivery delays.
• Skipping bleed on a full-image design. Without it, you’ll likely get a thin white border after trimming, which is easy to avoid by using the template.
• Burying your message or CTA in a low-contrast colour. If it’s not readable at a glance, it won’t be read at all.

Is Postcard Marketing Actually Effective?

According to JICMAIL’s Response Rate Tracker, the UK’s independent direct mail measurement body, warm direct mail (to existing customers) averages a 7.2% response rate, while cold mail to new prospects averages around 0.9%. The gap matters: postcards work best as a tool for staying in touch with people who already know you, a repeat customer list, past enquirers, or local regulars, rather than as a cold-outreach tool to strangers. 

As with any benchmark, actual results vary significantly by audience, offer, and industry, so treat this as a general guide rather than a guarantee.

Do You Need Consent to Send Marketing Postcards?

Unlike email or SMS marketing, postal marketing isn’t covered by PECR (the regulations that require opt-in consent for electronic marketing), so you don’t need explicit consent in the same way you would for an email campaign. 

However, UK GDPR and the Data Protection Act 2018 still apply whenever you’re using someone’s name and address for marketing; you’ll need a valid lawful basis (commonly “legitimate interests” for postal marketing), and recipients retain an unconditional right to object to receiving marketing mail at any point. This is a general pointer rather than legal advice. If you’re running a data-driven mailing campaign at any scale, it’s worth a quick check with a data protection advisor to make sure your specific approach is compliant.

Adding a QR Code for Trackable Responses

If you want to measure how well a marketing postcard performs, a QR code linking to a dedicated landing page (rather than your general homepage) lets you track scans and attribute responses directly to that mailing. Keep it a reasonable size (at least 2cm x 2cm) and away from the fold or trim edge so it always scans cleanly.

Get Your Postcards Printed at Banana Print

Whether it’s a personal note or a marketing mailer, we print postcards on 350gsm silk or recycled board, in matte or gloss, and dispatch them within one working day, with next-day delivery for £4.95. Browse our postcard templates or upload your own design to get started.

 

 

Start your design now → 

 

 

 

Postcard Design FAQs

What size should a postcard be to post at the cheaper Royal Mail rate? 

To qualify for the Letter rate, a postcard needs to be no larger than 240mm x 165mm, no thicker than 5mm, and no heavier than 100g. A standard A6 postcard (105mm x 148mm) fits comfortably within these limits.

Does an A5 postcard cost more to post than A6? 

Yes. A5 (148mm x 210mm) exceeds the 165mm width limit for the Letter rate, so it’s charged at the pricier Large Letter rate instead, even though it’s still just a flat postcard.

Where does the address go on a postcard? 

Conventionally, the recipient’s address goes on the right half of the back, with the stamp in the top-right corner. Your message goes on the left half.

Do I need bleed on my postcard artwork? 

Only if your design runs to the edge of the card (a full photo or background colour). Add 3mm of bleed beyond the final trim size on all sides, and keep text at least 4-5mm inside the trim line.

What paper is best for postcards? 

A sturdy cardstock, 350gsm or similar, holds up well in the post without needing extra reinforcement. Silk board gives a smooth, premium finish, while a recycled board suits a more eco-conscious brand.

How long does it take for a postcard to arrive in the UK? 

First class aims to arrive the next working day. Second class aims for two to three working days, though since Royal Mail’s April 2026 delivery reforms, second class mail (postcards included) is now delivered on alternate weekdays rather than daily in most areas, so it’s worth allowing a little extra time versus what you might expect from previous years, especially for time-sensitive marketing mailings.

What happens if my postcard doesn’t have enough postage? 

Royal Mail will still deliver it, but the recipient is charged a surcharge, not the sender. This makes double-checking your postcard’s size, thickness, and weight before posting worth the extra minute, especially for a mailing list where the same mistake would repeat across every card sent.

Do I need to include a return address on a postcard? 

It’s not compulsory, but Royal Mail recommends it. Without one, a postcard that can’t be delivered (wrong address, moved recipient) simply can’t be returned to you; it’s effectively lost.