The 2026-07-24 run covered these exact cartons on this exact lane. Your box and your ZIPs will read differently.
Four large cartons
| Box and weight | USPS | UPS | FedEx | Cheapest |
|---|---|---|---|---|
| 24 × 18 × 18 in, 30 lb | not offered | $43.77 Ground | $57.23 FedEx Ground Economy | $43.77 UPS Ground |
| 30 × 20 × 20 in, 40 lb | not offered | $77.56 Ground | $96.47 FedEx Ground Economy | $77.56 UPS Ground |
| 36 × 24 × 18 in, 50 lb | not offered | $95.62 Ground | $118.87 FedEx Ground Economy | $95.62 UPS Ground |
| 48 × 24 × 12 in, 35 lb | not offered | $86.45 Ground | $108.49 FedEx Ground Economy | $86.45 UPS Ground |
Large cartons are where the ground networks separate from the mail. USPS returned nothing on these boxes on this run, and the spread between the cheapest and the most expensive quote is bigger than the price of the small boxes entirely.
Why the price jumps
| Box | Actual weight | Dimensional weight (÷139) | Length + girth | Cheapest quote |
|---|---|---|---|---|
| 24 × 18 × 18 in | 30 lb | 55.9 lb | 96 in | $43.77 |
| 30 × 20 × 20 in | 40 lb | 86.3 lb | 110 in | $77.56 |
| 36 × 24 × 18 in | 50 lb | 111.9 lb | 120 in | $95.62 |
| 48 × 24 × 12 in | 35 lb | 99.5 lb | 120 in | $86.45 |
Every box above is billed on dimensional weight, not on the scale. That is the whole game with large parcels: an inch off each side is worth more than a pound out of the box.
Common questions
What counts as a large package?
Practically, anything past about 24 inches on the long side or past 30 lb. Carriers add oversize charges past 130 inches in length plus girth and refuse parcels past 165 inches or 150 lb.
What is the cheapest way to ship a large package?
On this run UPS Ground was cheapest on all four large cartons, from $43.77 for a 24 × 18 × 18 in 30 lb box to $95.62 for a 36 × 24 × 18 in 50 lb box. USPS returned no rate for any of them.
Is it cheaper to send two smaller boxes?
Often yes. Once you add up dimensional weight plus the oversize charge, a pair of 20 lb boxes will frequently come in under a single 40 lb one. Price it both ways before the tape goes on.
When does it stop being a parcel and become freight?
Past 150 lb, past 108 inches in length, or when the item needs a pallet. SMKlog sells parcel labels only.
Does the carrier really measure my box?
Yes. Automated dimensioners scan parcels in the sort hubs, and an under-declared box comes back as a billing adjustment after delivery. Measuring the finished carton honestly costs nothing and removes the surprise.