Best Pick
eBay Brand Central14.5" x 18.5" Polyjacket/Polymailer — 400 Envelopes
14.5″ × 18.5″ × 0″
+$0.00 Seller Free shipping · 3 lb billed
$0.290
landed per box
pack of 400 · $116.00
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⚠ DIM +9 lb100% Perfect fitBuy →
⚠ DIM +17 lb84% Snug fitBuy →
⚠ DIM +9 lb100% Perfect fitBuy →
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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
eBay Brand CentralBuy →
Buy + Easy Reshape⚠ DIM +5 lb25 ~ 24x8x6" Corrugated Kraft Cardboard Cartons Shipping Packing Box Boxes
24″ × 8″ × 6″
+$0.00 Seller Free shipping · 7 lb billed
$1.81
landed per box
pack of 25 · $45.25
⚠ DIM +9 lb100% Perfect fit50 - 18 x 12 x 8 Corrugated Shipping Boxes Storage Cartons Moving Packing Box
18″ × 12″ × 8″
+$0.00 Seller Free shipping · 11 lb billed
$1.84
landed per box
pack of 50 · $92.00
⚠ DIM +17 lb84% Snug fitGRAINGER APPROVED 11A767 PK 25 Shipping Box,18x14x12 in 11A767
18″ × 14″ × 12″
+$9.99 Seller Calculated · 19 lb billed
$1.86
landed per box
$1.32 each
pack of 25 · $33.00
⚠ DIM +9 lb100% Perfect fitGRAINGER APPROVED 55NM76 PK 25 Shipping Box,18x12x8 in 55NM76
18″ × 12″ × 8″
+$9.99 Seller Calculated · 11 lb billed
$1.89
landed per box
$1.49 each
pack of 25 · $37.25
⚠ DIM +9 lb100% Perfect fit25 - 18 x 12 x 8 Shipping Boxes Packing Moving Storage Cartons Mailing Box
18″ × 12″ × 8″
+$0.00 Seller Free shipping · 11 lb billed
$2.06
landed per box
pack of 25 · $51.50
Showing 6 of 26 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 **landed cost per box** — the pack price plus shipping, divided by the number of boxes. A 100-pack with $10 shipping works out cheaper per box than a 25-pack with the same shipping, because the fixed cost spreads further. Every listing below links to a real product page from eBay, ULINE, or other retailers; 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.