Mailer Boxes

Custom Mailer Boxes

Custom mailer boxes are self-locking corrugated shipping boxes printed with your branding, built to go into the mail without an outer carton. We produce them in kraft or white liner, with printing inside and out, tape-free interlocking construction, and a free dieline drawn to your product. Orders start at 200 units with production in 8 to 12 days.

The dimensions matter more than most brands realise, and not for aesthetic reasons. Carriers bill on box volume, so an oversized mailer costs you money on every single order for the life of the SKU. We size mailers to the product, then tell you what that sizing does to your shipping bill.

Box Size Is a Shipping Cost, Not Just a Design Choice

Carriers charge the greater of your parcel’s actual weight or its dimensional weight, calculated as length × width × height divided by a divisor. This is the single most expensive thing brands get wrong when ordering mailers, and it got noticeably more expensive in 2026.

What changed: on 12 July 2026, USPS cut its dimensional weight divisor from 166 to 139, matching UPS and FedEx, and adopted round-up-every-dimension rules. For a package over one cubic foot, that raised dimensional weight by roughly 19% overnight. USPS applies dimensional weight only above 1,728 cubic inches, while UPS and FedEx apply it to every parcel regardless of size.

What the round-up rule means in practice: every fractional dimension bills up to the next whole inch before the maths runs. An 11.2″ box side is billed as 12″. Three round-ups on one box can add 15 to 20% to the computed volume with no change in the published rate.

Dimensional weight at divisor 139, for common mailer footprints:

Look at rows three and four. One inch added to each dimension moves a 12 × 9 × 4 mailer from four billable pounds to five. On 500 orders a month, that’s a cost you’re paying every month purely because the box was drawn a little loose.

Send us your product dimensions and we’ll draw the mailer to the smallest size that still protects it, then show you the dimensional weight of the result before you commit to a print run. Carrier rules change with annual rate updates, so confirm current figures against your own carrier agreement.

Right-Sizing: The Trade-Off Nobody Explains

Smaller isn’t automatically better. A mailer that’s too tight crushes product and jams during pack-out, so throughput drops and your team starts forcing lids. A mailer that’s too loose costs you three ways at once: dimensional weight on every order, void fill to stop the product moving, and damage claims when it moves anyway.

The working range for most products is around a quarter-inch of clearance per side, plus whatever your insert or tray occupies. Tell us:

• Product dimensions at the widest point, not the nominal size
• Whether anything else goes in the box (tissue, card, sample, insert)
• Whether you pack by hand or on a line
• Your typical monthly order volume

That last one matters because it decides whether right-sizing is worth a tooling change. At 200 orders a month, a slightly loose box is a rounding error. At 5,000, it’s a budget line.

Mailer Styles

• Roll end tuck top (RETT): the standard ecommerce mailer. One piece, folds flat, locks closed with no tape.
• Roll end tuck front: front-locking variant, slightly easier one-handed close during pack-out.
• Roll end with double side wall: extra layer along both long sides, for heavier or more fragile contents.
• Tuck top with tear strip: built-in perforated strip so the customer opens it cleanly without a knife.
• Returns-ready mailer: a second adhesive strip and second tear line, so the same box goes back for a return. Worth costing if you’re in apparel or footwear, where return rates make a second box a real expense.
• Snap lock bottom: locking base for denser products.
• Book and literature wrap: wraps to the depth of the contents, so a thin item ships thin rather than in a half-empty box.
• Full-telescoping two-piece: base and lid for premium or gifting shipments.

Board Specification for Parcel

A mailer has to survive a carrier network, which is a different requirement from sitting on a shelf.

Specify ECT, not just flute. Edge Crush Test rating measures compression strength, and two boards with the same flute profile can perform very differently. 32 ECT single-wall covers most parcel shipping. If you’re shipping glass, ceramics or liquids, ask us to quote double-wall alongside single-wall so you can weigh board cost against damage claims.

One note on print: upgrading to a white or clay-coated liner on the same flute usually improves colour fidelity more than switching flute profile does, and it’s often cheaper.

Materials and Finishing

• Natural kraft liner: uncoated, recyclable, the default for sustainability-led brands. Cheapest option and the print looks deliberately raw rather than cheap.
• White liner: for full-colour artwork, photography and gradients
• Interior printing: a message, care instructions or a discount code on the inside face. The highest-impact, lowest-cost upgrade available on a mailer, because it’s the surface your customer sees at the moment of opening.
• Coatings: matte, gloss or soft-touch lamination
• Foil stamping and embossing: available on litho-laminated builds
• Die-cut windows: product visible before opening
• Printed sleeves: seasonal messaging over a plain mailer, reprintable without a new box run
• Labels and stickers: the cheapest route to branding a plain kraft mailer, and worth costing against full print

Printed mailer or plain kraft plus a sticker?

If you’re under a few thousand units a year, a plain kraft mailer with a well-designed sticker and printed tissue often lands closer to a fully printed box than people expect, at a fraction of the print setup. We’ll quote both. The fully printed mailer wins on impact, but you should see the gap in real numbers before deciding.

What Our Customers Say

“Really impressed with the quality of my packaging. The Grand Packaging delivered results that truly exceeded my expectations. Working with Daniel was super smooth. The design support was amazing, customer service was excellent, and overall the experience was very positive.” — Debbie Muller, Designer

“Custom soap boxes. Daniel was great to work with: professional, knowledgeable, and helpful throughout the process. My order arrived earlier than expected, and I truly appreciated his guidance on sizing and setting up the artwork correctly. Highly recommended!” — Ava Nicole, Manager, soap and skincare brand

Who We Produce Mailers For

• Ecommerce and DTC brands shipping direct from their own warehouse or a 3PL
• Subscription boxes needing a consistent monthly format and predictable freight cost
• Apparel and footwear where returns-ready construction earns its keep
• Beauty and skincare shipping bottles and jars that need inserts
• Food and specialty goods where the mailer travels with an inner retail box
• PR and gifting teams sending seeded product and press kits

Pricing and Minimum Order Quantity

The minimum order for custom mailer boxes is 200 units. Double-wall construction and some finishing processes need a higher run to be viable, and your consultant will confirm for your spec.

Price is driven by quantity, dimensions, board grade, print coverage and finishing. Interior printing counts as an additional print side. Dimensions affect both the box price and, separately, every shipping label you buy afterwards.

Why we quote by project rather than showing a calculator

Configurators price from a fixed list of sizes, which is exactly the wrong approach for a mailer. The whole point of a custom mailer is that it’s drawn to your product rather than rounded up to the nearest preset, and rounding up is what generates dimensional weight charges. Picking the closest stock size defeats the reason for ordering custom in the first place.

Every quote is itemised by board, print and finishing so you can compare it line by line against another supplier. Most quotes go out the same business day.

First-time customers currently receive 20% off their first order.

How Your Order Is Produced

1. Send your product dimensions and requirements. Widest measurements, what else goes in the box, quantity, board preference and finish.
2. Receive your quote and dieline. Drawn to your product at no additional cost, with the dimensional weight of the finished size confirmed.
3. Place artwork and approve the proof. Our team checks bleed, colour mode, resolution, fold lines and interior print placement.
4. Request a physical sample (optional). Order within 30 days of receiving it and the sample cost is credited back. On mailers specifically, pack your actual product into the sample before approving, since fit and pack-out speed only show up in a real box.
5. Production. Printing, lamination, die-cutting and gluing.
6. Quality check and dispatch. Shipped flat, ready to fold.

Standard production runs 8 to 12 days after proof approval, plus transit. Double-wall builds and specialty finishes take longer. Tell us your deadline at quote stage.

Why Ecommerce Brands Order Mailers From Us

• We size for freight, not just fit. You get the dimensional weight of your mailer before the print run, not after your first month of shipping invoices.
• Board specified against contents. Flute and ECT chosen for what you’re actually shipping, with double-wall quoted alongside single-wall when it’s a close call.
• Cheaper alternatives quoted honestly. If a kraft mailer with a sticker gets you 80% of the result for 40% of the cost, we’ll show you that comparison.
• Design support included. Artwork checked and corrected before press, including interior print placement.
• Sample credited back. Pack your real product into a real box before committing.
• One named contact. The same consultant across every reorder and every new SKU size.
• US-based support. Quotes, proofs and phone support in US hours from our St. Petersburg, Florida office.

Request a Quote for Custom Mailer Boxes

Send your product dimensions and monthly volume. We’ll come back with a mailer sized to the product, the dimensional weight it carries, and an itemised price.

Call: +1 (630) 228-1764 Email: sales@thegrandpackaging.com Hours: Monday to Friday, 9:00 am to 5:00 pm ET

Not sure whether you need a mailer or a retail box? Our guide to mailer boxes vs retail boxes covers when each one applies.