Best Pick
eBayeBay Brand Central
14.5" x 18.5" Polyjacket/Polymailer — 400 Envelopes
14.5″ × 18.5″ × 0″
+$12.40 USPS Ground Advantage · 3 lb billed
$0.29
each
$0.321 landed
pack of 400 · $116.00
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Cheapest 18×12×8 padded mailer
Compare real eBay prices for 18×12×8 shipping boxes with DIM-weight-aware shipping estimates.
Live listings — sorted by landed cost per box
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eBay⚠ DIM +11 lb
GRAINGER APPROVED 55NM76 PK 25 Shipping Box,18x12x8 in 55NM76
18″ × 12″ × 8″
+$28.50 UPS Ground · 13 lb billed
$1.49
each
$2.63 landed
pack of 25 · $37.25
eBay⚠ DIM +17 lb
GRAINGER APPROVED 11A767 PK 25 Shipping Box,18x14x12 in 11A767
18″ × 14″ × 12″
+$36.10 USPS Ground Advantage · 19 lb billed
$1.32
each
$2.76 landed
pack of 25 · $33.00
eBay⚠ DIM +11 lb
GRAINGER APPROVED 55VH40 PK 25 Shipping Box,18x12x8 in 55VH40
18″ × 12″ × 8″
+$28.50 UPS Ground · 13 lb billed
$2.19
each
$3.33 landed
pack of 25 · $54.75
eBay⚠ DIM +11 lb
18x12x8 Corrugated Shipping Boxes 25/pk
18″ × 12″ × 8″
+$28.50 UPS Ground · 13 lb billed
$2.30
each
$3.44 landed
pack of 25 · $57.50
eBay⚠ DIM +17 lb
18x14x12 Corrugated Shipping Boxes 25/pk
18″ × 14″ × 12″
+$36.10 USPS Ground Advantage · 19 lb billed
$2.24
each
$3.68 landed
pack of 25 · $56.00
Showing 6 of 25 real listings. Want all of them with custom quantity and weight? Search now →
What fits in a 18×12×8 box
A 18 × 12 × 8 inch box holds 1,728 cubic inches (1.00 cu ft) of interior space, putting it in the large-category. It's a popular choice for shipping items like multiple pairs of shoes, small appliances, clothing bundles — things that fit comfortably within those dimensions while leaving room for protective padding. Large boxes at this size are usually sold in smaller bulk packs — 10 to 25 — because storage and shipping of the empty stock itself becomes a consideration.
Shipping math for this size
Shipping cost for this size depends heavily on dimensional weight. For a 18×12×8 box, UPS and FedEx Ground compute a DIM weight of 13 lbs using their 139 divisor, while USPS Ground Advantage uses a 166 divisor, giving 11 lbs. Carriers bill whichever is greater — your actual weight or the DIM weight. USPS's higher divisor makes it roughly 2 lbs cheaper than UPS/FedEx for this size when your item is light, which is why our search results factor in DIM-weight automatically instead of just showing sticker prices.
How to pick the right pack size
When buying a 18×12×8 box, the biggest cost lever isn't which retailer you pick — it's which pack size you commit to. A 100-pack typically costs 2-3× more than a 25-pack but brings the per-unit cost down by 40-60%. Our ranking is based on *cost per useful box*, which gives bonus boxes partial credit — so a 100-pack can still win for single-box needs if the per-unit price is low enough, but a 25-pack often ranks higher when you only need a few. Every listing below links to a real eBay product page; we don't show placeholder results.
Search with your own dimensions
Pre-filled with 18×12×8. Adjust weight, quantity, or size as needed — we'll re-rank for your exact scenario.