Envelope Printing & Business Mailing: Sizes, Types & What to Print

Envelope sizes pair with paper sizes: DL takes an A4 letter folded in thirds, C5 takes A4 folded once (or A5 flat), C4 takes A4 unfolded. Printed envelopes — your logo and return address on the face or flap — turn every piece of post into a brand impression and measurably improve open attention for direct mail.

Envelope sizes decoded

Envelope	Size	Takes	Typical use
DL	110 × 220mm	A4 folded ×2	letters, invoices, compliment slips
C6	114 × 162mm	A6 card / A4 folded ×4	greetings cards, RSVPs
C5	162 × 229mm	A4 folded once, A5 flat	brochures, unfolded A5 pieces
C4	229 × 324mm	A4 flat	certificates, unfolded documents, photos

(The C-series is sized exactly to wrap the matching A-series sheet.)

Window or plain?

Window envelopes show the address printed on the letter itself — no labels, no separate address run, and the standard for invoices from any system that prints addresses in the window position. Plain suits anything personal or premium, addressed by print or hand.

Printed envelopes vs address labels

Printing the envelope (return address + logo, usually top-left or on the flap) looks established and saves sticking labels forever after. Labels win only for tiny volumes or when envelope stock keeps changing. For regular posters of mail — solicitors, accountants, clinics — printed envelope stock pays for itself in time alone.

Practical mailing notes (UK)

Royal Mail prices by size band: Letter (up to 240 × 165mm and 5mm thick — DL and C6 fit), Large Letter (up to 353 × 250mm and 25mm — C5 and C4), then parcels. Two design implications: square envelopes price as Large Letters despite their size, and a heavy insert can push a Letter into a higher band — weigh a made-up sample before committing a mailing to the budget.

Matching the set

Envelopes complete the stationery set — same stock family and design language as the letterhead. Coloured or kraft envelopes lift response on direct mail simply by not looking like every other white envelope in the pile.

FAQs

What envelope fits an A5 flyer without folding? C5 (162 × 229mm) — an A5 piece slides in flat.

Can you print full-colour designs on envelopes? Yes — faces and flaps print in full colour; heavy full-bleed coverage is best discussed first as some envelope constructions handle it better than others.

What's cheapest to post? Anything within Letter size (DL/C6, under 5mm thick, under 100g). Design mailers backwards from that band when volume is high.

Do you print envelopes in Ipswich? Yes — DL to C4, plain and window, quoted by quantity: minutemanpressipswich.co.uk, 01473 933888.