Packaging · bag sizing
Poly mailer size calculator.
Enter a folded product's width, length and thickness. Get the minimum flat bag size and the smallest common mailer sizes that clear it.
Folded product
Minimum bag and nearest sizes
Enter product dimensions.
How the size is worked out
With stack thickness T (thickness × quantity), the minimum flat bag is:
- Width = product width + T × 2 × k + seal allowance
- Length = product length + T + flap allowance
The default k = 0.5 is the pure geometry of a flat tube wrapped around a rectangle: the bag's flat width must cover half the product's perimeter, (2 × width + 2 × T) ÷ 2 = width + T. Raise k to leave slack for a soft or bulging product. The default seal (0.5 in) and flap (2 in) are assumptions of this tool, not manufacturer specifications. Replace them with the figures from your supplier's spec sheet.
Size list and bands
The list is the nominal width × length of Uline's tear-proof polyethylene mailers: 6×9, 7½×10½, 9×12, 10×13, 12×15½, 14×17, 14½×19, 19×24, 24×24 and 24×36 in (Uline catalog page, read 2026-09-30). Other suppliers and bubble mailers use different sizes. Suppliers differ on whether the stated length includes the flap, so this tool compares the nominal size to the full requirement including flap. Check the spec sheet.
Bands are this tool's own rule of thumb using the tighter axis: tight is the required size at 90% or more of the bag, workable is 75-90%, generous is under 75%.
Test before you order
This is flat geometry only. It ignores compressible or bulging products, corners, seal width variation and film stretch. Pack a real sample in a real bag, seal it, and check it before buying in bulk.