Postcards are a popular format for both personal and promotional use, but not everyone knows their exact dimensions. Whether you're designing one for printing, sending one through the post, or simply collecting them, knowing the correct size is key. The size of a postcard can vary slightly depending on the country and purpose, but there are standard dimensions that most printers and postal services follow.
Postcards are designed to be compact, sturdy, and suitable for mailing without an envelope. This means they need to meet certain size requirements to qualify for standard postage rates, particularly if being sent through Royal Mail or similar postal services.
Most postcards fall within a close range of sizes, but if a card is too small, it may be classed as non-mailable. If it’s too large, it may require more expensive postage or be treated as a letter instead.
Standard Postcard Size UK
In the UK, the most common postcard size is A6, which measures 10.5 x 14.8 cm or 4.1 x 5.8 inches. This size strikes a balance between being large enough for an image and message, while still qualifying for the standard letter postage rate with Royal Mail.
Some postcards are printed slightly larger — such as 5 x 7 inches (12.7 x 17.8 cm) — which is common for artistic or photographic cards. These can still be posted but may cost slightly more to send, depending on thickness and weight.
Postcards used for marketing, real estate or direct mail campaigns may vary in size, but for them to be posted economically in the UK, they typically need to remain within Royal Mail’s letter dimensions. That means no more than 24 cm in width, 16.5 cm in height, and 5 mm in thickness.
The paper used for postcards is usually heavier and coated on one side to support printing while leaving space on the back for a message and address. Finishes can vary from matte to glossy, but the structure remains the same: a simple, sturdy card designed to deliver a message efficiently.
Postcard sizes around the world
While A6 (105 x 148 mm) is the standard in the UK and many parts of Europe, postcard sizes do vary internationally. In the United States, for example, a typical postcard is 4 x 6 inches (101.6 x 152.4 mm), which is slightly wider and shorter than A6. This difference can matter if you're printing postcards for international mailing or expecting to meet certain postal specifications.
Another popular size globally is DL (99 x 210 mm) — the same width as an A4 page folded into thirds. It’s less common for casual postcards but widely used in promotional mailings.
Minimum and maximum postcard sizes for mailing
In the UK, Royal Mail considers a postcard as a standard letter as long as it fits within their set dimensions:
- Minimum size: 14 cm x 9 cm
- Maximum size: 24 cm x 16.5 cm
- Maximum thickness: 5 mm
Anything outside these boundaries may be charged at large letter or parcel rates. So if you're designing a custom postcard, make sure it sits comfortably within this range to avoid extra charges or delivery issues.
Postcard bleed and trim areas (for printing)
If you're printing your own postcards, it's important to understand the concept of bleed and trim. To ensure there are no white edges, printers usually ask for an extra 3 mm bleed around each side of the design. That means for an A6 postcard (105 x 148 mm), you should supply artwork sized at 111 x 154 mm, with all important text or images kept within a safe area, slightly inset from the trim line.
This ensures nothing important gets cut off during printing and trimming.
Thickness and material
Postcards are typically printed on thicker card stock, usually between 250 gsm and 400 gsm. Anything thinner risks being bent or damaged in the post. Some postcards are coated on one side — often gloss or silk — while the reverse is left uncoated so it’s easy to write on.
For premium postcards or keepsakes, heavier card and lamination can be used, but that may increase weight and postage cost.
Framing and displaying postcards
Because A6 is a standard frame size, it’s also popular for display purposes. Many people collect postcards from travel or art exhibitions and mount them in multi-aperture frames, shadow boxes or clip frames. If the postcard has an unusual size, custom mounts can be used to help them fit standard frame sizes like A5 or 6x4 inches.
Summary
In the UK, the standard size for a postcard is A6, which is 10.5 x 14.8 cm. While other sizes like 5 x 7 inches are also used, A6 remains the most widely accepted for postal use. Whether for travel, marketing or design, knowing the right postcard dimensions helps you stay within postal rules and ensures your message arrives looking its best.
