If you're setting up a label printer for the first time, or switching from printing on A4 sheets to a dedicated thermal printer, the label size question comes up fast. Most UK courier platforms give you a few size options without explaining which one actually matters, and the terminology (4x6, 6x4, 100x150mm) can make it look more complicated than it is.
This guide covers what size shipping labels you need for the main UK couriers, what the different size formats actually mean, and how to choose the right label for your printer and order volume.
The standard UK shipping label size
For the vast majority of UK courier and postal shipping, the standard label size is 4x6 inches, which is the same as 100x150mm. You'll also see this written as 6x4, which refers to the same dimensions just listed in the opposite order. There's no functional difference between 4x6 and 6x4; it's the same label, described both ways depending on the platform or supplier.
This size is used across Royal Mail, Evri, DPD, Hermes, UPS and most other UK delivery services. If you're printing shipping labels from Royal Mail Click and Drop, Shopify, eBay, Amazon, Vinted or any similar platform, 4x6 (100x150mm) is the format you need.
Our white thermal labels in 4x6 inch (100x150mm) are the standard choice for this and work with all major UK courier platforms and direct thermal printers.
Why 4x6 is the size almost everyone needs
The 4x6 format isn't an arbitrary standard. The size gives enough space for a courier barcode, the destination address, return address, service type and any tracking or routing codes, all at a size that scans reliably through automated sorting systems. Smaller labels can struggle to fit all of this information without shrinking the barcode to a size that risks scan failures. Larger labels waste material without adding any functional benefit for standard parcel shipping.
Royal Mail's Click and Drop platform offers a 6x4 separate label and despatch note template alongside A4 options, and this 6x4 format corresponds directly to the 100x150mm thermal label size. Evri and DPD use the same 100x150mm format across their business shipping platforms. If you're unsure which label size your account is set to output, check your label settings within the courier platform before ordering labels, as the platform setting needs to match the label size in your printer.
Royal Mail label size
Royal Mail Click and Drop supports a few label template options, but for anyone using a dedicated thermal printer, the relevant one is the 6x4 (100x150mm) separate label template. This produces a single label per parcel containing the address, postage details and barcode, sized to print directly onto a 4x6 thermal label with no trimming or folding required.
If you're printing on A4 sheets instead of a thermal printer, Royal Mail's A4 templates allow multiple labels per sheet, but this is a different workflow entirely and not something thermal label rolls are designed for. For anyone using or considering a thermal printer, 4x6 (100x150mm) is the Royal Mail label size to set up.
Evri label size
Evri's business shipping platform, like most UK couriers, outputs labels at 100x150mm as standard. When connecting Evri to an e-commerce platform or using their business portal directly, confirm the label format is set to 100mm width, which corresponds to the standard 4x6 thermal label. This applies whether you're printing through a direct Evri integration, a multi-carrier shipping tool, or exporting and uploading orders manually.
DPD label size
DPD and DPD Local also use the 100x150mm format for standard parcel labels. When setting up a DPD account with a thermal printer, the label format setting in your DPD account or integration should be set to 100x150mm to match a 4x6 thermal label. This is consistent across DPD's various integration methods, whether through a plugin, API connection or the DPD online portal.
Setting your printer and platform to match
The most common reason for label printing problems isn't the label itself, it's a mismatch between the label size loaded in the printer and the label size selected in the courier platform or shipping software. If your printer is loaded with 4x6 labels but the platform is set to output an A4 layout, you'll get a tiny portion of the label printed in the corner of a blank sheet, or nothing at all.
When setting up a new thermal printer, check three things: the label size physically loaded in the printer, the label size selected in the printer driver on your computer, and the label format setting within the courier platform or shipping software itself. All three need to match. Most setup issues come down to one of these three settings being left on a default that doesn't match the others.
Other thermal label sizes and what they're used for
While 4x6 covers the vast majority of shipping label needs, there are other sizes worth knowing about for specific applications.
4x4 inch labels
A square format, slightly smaller than 4x6. Used for some courier formats that don't require the full 6 inch length, for product labelling, and for some return labels where less information needs to fit. Some courier services that print a combined label and returns slip in one document may use this format. Our white thermal labels in 4x4 inch are a useful size to have on hand if your courier or platform calls for it, or for general warehouse and product labelling tasks.
4x2 inch labels
A smaller format used for product labels, barcode labels for inventory, small parcel labels where a full 4x6 isn't needed, and labelling smaller items, bins or shelves in a warehouse environment. Not typically used for full courier shipping labels, since the smaller area limits barcode size and address space, but useful as a secondary label format for businesses that need more than just shipping labels. Our white thermal labels in 4x2 inch work well for this.
Do you need different sizes for different couriers?
No. Because Royal Mail, Evri, DPD and most other UK couriers all standardise on 100x150mm (4x6) for parcel shipping labels, a single label size covers all of them. If you ship through multiple couriers, which is common for businesses using multi-carrier shipping platforms, you don't need to stock different label sizes for each one. The 4x6 format is genuinely universal across UK courier shipping.
The only reason to stock additional sizes is for non-shipping applications: product labelling, inventory barcodes, or smaller return labels where a platform specifically calls for a different format.
Roll labels vs fanfold for shipping
Once you've settled on 4x6 for your shipping labels, the next decision is roll or fanfold format. Both print identically and both work with the same printers. Roll labels are wound on a core and are the more common format for most setups. Fanfold labels are pre-cut and stacked in a concertina box, which suits higher-volume operations where you don't want to interrupt packing to change a roll partway through a batch.
For lower daily volumes, a roll of 4x6 labels is the simplest option. For higher volumes, fanfold reduces interruptions during a packing run. Either format will produce the correct Royal Mail, Evri or DPD label once your printer and platform settings match.
Thermal printer vs printing on A4
If you're currently printing shipping labels on A4 sheets and cutting or folding them to size, switching to a dedicated thermal printer with 4x6 labels removes that step entirely and produces a cleaner, more durable label with better barcode quality for scanning. We cover the comparison between the two approaches in more detail in our thermal printer vs A4 shipping labels guide, including when switching makes sense based on your order volume.
You can browse the full range of thermal labels, including 4x6, 4x4 and 4x2 sizes in roll and fanfold formats, on our thermal labels page.
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