The envelope is the part of the mailing that gets seen first
A Singapore company that still sends physical mail (statements, contracts, cheques, invitations, annual reports) sends most of it in envelopes that were ordered without much thought: whatever size the previous admin manager bought, with the logo wherever the previous print shop put it. Then a mailing goes out with the address showing at the wrong angle in the window, or the C4 envelopes turn out to be too small for the folder, and the job stops.
This guide covers the sizes that matter for Singapore corporate mail, the window positions that work with standard letter templates, what SingPost expects of a machineable envelope, the stocks and print methods, and how to set up a bulk order that lasts a year without running out of the one size everyone uses.
Sizes that a Singapore office actually needs
| Envelope | Size | Holds | Typical use |
|---|---|---|---|
| DL | 110 x 220 mm | A4 folded in three | Letters, statements, invoices, cheques |
| C5 | 162 x 229 mm | A4 folded in half, or A5 flat | Brochures, multi-page letters, cards |
| C4 | 229 x 324 mm | A4 flat | Contracts, reports, presentation folders (check the folder size first) |
| C6 | 114 x 162 mm | A6 card, A4 folded in four | Invitations, greeting cards |
| Square 155 or 160 | 155 x 155 mm | Square cards | Corporate invitations and festive cards |
Most companies need DL in volume, C5 and C4 in smaller numbers, and C6 or square once a year for the CNY or year-end card. The common mistake is ordering the same quantity of each. A DL runs out in months; a box of 500 C4 sits in the store for three years and yellows.
One sizing trap: a presentation folder is usually slightly larger than A4, around 220 x 310 mm, so it does not fit a C4 envelope with the flap closed. Ask for a "C4 plus" or a board-backed 250 x 353 mm envelope, or check the folder against a sample before ordering a thousand. Our guide to presentation folder sizes gives the dimensions.
Windows and where the address lands
A window envelope removes the addressing step entirely, which is the point, but only if the address block in the letter template lines up with the window on the envelope. Envelope windows are specified by position from the left and bottom edges, and by size. For a DL envelope, a common window is 45 x 90 mm, positioned 20 mm from the left edge and 15 mm from the bottom, matching a letter folded in thirds with the address block set in the top-left of the page.
Before ordering printed window envelopes, print the actual letter template, fold it, and put it in a sample envelope. Check that the whole address shows with at least 3 mm clearance on every side of the window, and that no other text (the letterhead, a reference number) is visible through the window; SingPost's sorting equipment reads whatever it sees. If the template and the window disagree, changing the template is usually cheaper than a custom window position, unless you are ordering in the tens of thousands.
Postal requirements
SingPost publishes specifications for mail that can go through automated sorting, and staying inside them avoids surcharges and delays on a bulk mailing. The points that affect envelope design:
- The address area should be clear of any printing other than the address, and the bottom 15 mm or so of the envelope should be kept free for the postal barcode.
- The right-hand portion of the front is for the stamp or postage impression; keep artwork out of it.
- Light-coloured envelopes with dark address text read best. A dark navy envelope with a white window is a design statement that may end up hand-sorted.
- Envelopes should be rectangular, with an aspect ratio in the accepted range; square envelopes generally count as non-standard and cost more to post.
Check SingPost's current guidelines for exact dimensions and clearances before a large print run; they are updated from time to time and the postal service, not the printer, decides what qualifies for the standard rate.
Stock, seal and print method
- Paper. 100 gsm white wove is the corporate standard for DL and C5. 120 gsm for C4, or a board-backed C4 for documents that must not bend. Kraft (brown) is an option for a warmer look, but the logo colour shifts on it.
- Seal. Peel-and-seal (a strip of adhesive under a liner) is what an office wants for volume; gummed flaps need moistening; self-seal (two latex strips that stick to each other) is quick but has a shelf life of about a year in Singapore humidity.
- Security tint. A printed pattern inside the envelope that stops the contents being read through it. Standard for statements and anything with personal data.
- Print method. Envelopes are printed either flat before they are made (offset, best quality, higher minimums, longer lead time) or pre-made through a digital or offset envelope press (lower minimums, from a few hundred). A one- or two-colour logo on the flap or top-left corner is the normal corporate job; full-bleed designs need flat printing before conversion.
Ordering in bulk without waste
Envelope orders are cheap per unit at 5,000 and above and expensive per unit below 500, which pushes people to over-order. A practical approach:
- Count last year's usage from the mailroom or the purchasing records, by size. Order 12 months of DL, 6 months of C5 and C4.
- Keep the artwork to a one- or two-colour logo and the return address. A rebrand or an office move then requires only a small reprint rather than the loss of a large stock.
- Store envelopes flat in the original cartons, in air-conditioned space. Humidity curls the flaps and sets off the gum on self-seal envelopes.
- Set a reorder point (for example, when the last two cartons are opened) and record it in the same way as other printed stock; our guide on storing and reordering printed stock gives a method.
Corporate envelope printing with us
We print DL, C5, C4 and specialty envelopes for Singapore companies from a few hundred upward, with or without windows, in standard or custom window positions, with peel-and-seal and security tint as options. Send us your letterhead template and we will supply a sample envelope to check the window alignment before the run, and we hold your artwork on file so a repeat order is a one-line email.
For companies that mail in volume, we can supply envelopes pre-packed in mailing quantities and, with our custom printing service, handle the letter print and insertion as one job. See the full stationery range under general printing, or contact us with the sizes and annual quantities for a quotation.
