Avoid costly direct mail mistakes and get the best postage rates with this USPS cheat sheet

At Neyenesch Printers, we want your direct mail to be powerful and postal-compliant. One small design detail can bump your postage costs or delay your campaign, so understanding the basics of USPS requirements can save you time, money, and headaches. Whether you’re mailing postcards, booklets, or folded self-mailers, here’s what you need to know:

Mail Piece Categories (and Why Size Matters)

Your direct mail piece type determines how much you’ll pay in postage and what USPS regulations apply. Here’s a breakdown:

• Postcards
  • Size: 3.5″ x 5″ to 4.25″ x 6″
  • Only qualifies for First-Class Mail
  • Must be at least .007″ thick
  • Aspect ratio (length ÷ height) must be between 1.3 and 2.5
• Letters
  • Size: 3.5″ x 5″ to 6.125″ x 11.5″
  • Includes larger postcards and envelopes
  • Thickness: .009″ to .25″
  • Available in all mail classes
  • Follows same aspect ratio as postcards
• Self-Mailers
  • Size: 3.5″ x 5″ to 6″ x 10.5″
  • Folded pieces with no envelope
  • Paper stock: 70# minimum (under 1 oz), 80# (over 1 oz)
  • Same aspect ratio rules
• Booklets
  • Multiple pages bound (e.g., saddle-stitched)
  • Size: 3.5″ x 5″ to 6″ x 10.5″
  • Cover stock: 40#–80#, depending on design
  • Available in all mail classes
  • Same aspect ratio applies
• Flats
  • Size: 6.126″ x 11.51″ up to 12″ x 15″
  • Thicker mail like catalogs
  • No aspect ratio requirement
  • Minimum paper thickness: .009″

Addressing Guidelines

Proper address placement is critical. Here’s how to stay in USPS compliance:

• Postcards, Letters, Self-Mailers & Booklets:
  • Address block must be 4″ x 2″ with no varnish, coating, or images
  • Keep it .5″ from the right edge and .625″ from the bottom
  • Clear of graphics by .125″
  • Barcode can go in address block or in the bottom 5/8″ “barcode clear zone”
• Flats:
  • Address block must be in the top half of the short edge
  • Barcode must be within the address block
  • Same 4″ x 2″ clear zone rules apply

Folding, Tabbing & Gluing Rules

This is where things get sticky, literally.

• Self-Mailers
  • Horizontal fold: final fold is below the mail panel
  • Vertical fold: final fold is to the right of the mail panel
  • Tabbing/glue required:
    • ≤1 oz: two 1″ tabs
    • 1 oz: two 1.5″ tabs
    • Fugitive glue: use 3–4 spots or lines, 1/8″ wide or 3/8″ diameter
• Booklets
  • Binding can be on the bottom or right of the mail panel
  • Requires 3 non-perforated tabs (1.5″ diameter):
    • Bottom binding: two tabs right, one left
    • Right-side binding: two tabs above, one left
• Flats
  • No tabs or gluing needed (unless polybagged)
  • Fold or bind to the right of the mail panel (unless in envelope)

Pro Tip: Always Pre-Check with Us

Even experienced marketers get tripped up by USPS technicalities when designing direct mail. Our advice? Send us your PDF design before you finish. We’ll help you flag any issues before they cost you money.

Got questions or a campaign coming up? We’re here to help your mail make it to its destination, efficiently, affordably, and beautifully. (619) 297-2281 or contact@neyenesch.com