DL envelopes are one of the most recognised and widely used envelope sizes in the UK, especially for business and formal correspondence. They’re ideal for posting letters, invoices and forms folded neatly into thirds. This long, slim format is a standard in office environments and is perfectly designed to work with A4 paper.
The DL size is part of the international envelope sizing system and is often used for windowed envelopes, marketing materials, and formal documents where presentation and mailing efficiency matter.
Standard DL envelope size in centimetres and inches
The standard DL envelope measures 11 centimetres by 22 centimetres, which is approximately 4.3 inches by 8.7 inches. This size is specifically designed to hold an A4 sheet folded twice into three equal parts along its length. The result is a clean, compact format that slides easily into the envelope without needing to be forced or trimmed.
The long, rectangular shape of a DL envelope also makes it ideal for printing return addresses, postal details and branding in a tidy, professional layout.
What fits into a DL envelope
DL envelopes are made to fit one-third of an A4 sheet, which makes them perfect for standard letters, statements, invoices and application forms. You can also use them for invitations, flyers or leaflets that are designed in a long, narrow format. Businesses often use DL envelopes for outgoing post that includes covering letters, bills or service updates.
Many DL envelopes come with a window, allowing addresses to show through from the folded document inside, which makes bulk mailing faster and more efficient. You can also find DL envelopes with peel-and-seal or gummed closures depending on your preference.
DL envelope postage and use
DL envelopes generally qualify for standard letter postage in the UK, making them a cost-effective choice for both personal and business mailing. As long as the contents remain under 100 grams in weight and 5 millimetres in thickness, they fall within Royal Mail’s standard letter size range.
They are widely used across industries due to their compatibility with printers and folding machines, which makes them suitable for high-volume mailing. Whether you're sending a single letter or a mass communication, the DL envelope is an efficient and professional-looking option.
Summary
A DL envelope measures 11 by 22 centimetres and is designed to hold an A4 sheet folded into thirds. It’s the go-to size for business letters, invoices, and formal documents, offering a clean, compact and cost-efficient way to mail important information. The DL format is simple, reliable and widely accepted across all types of correspondence.