Measure the packed box before you name a shipping price: on a big carton the size decides the bill, not the weight.
Why ground beats the post office here
Three rules decide what a heavy second-hand item costs to send, and all three work against a big box at the post office.
- Above one cubic foot (1,728 cubic inches), USPS, UPS and FedEx all bill the larger of the real weight and the box size: length x width x height divided by 139, rounded up to the next pound.
- USPS adds a nonstandard fee once a box passes two cubic feet, so a carton holding an amplifier or a speaker pays twice for its size.
- USPS takes parcels up to 70 lb and 130 inches in length plus girth. UPS and FedEx take up to 150 lb and 165 inches, which is the room a heavy item needs once it is padded.
None of this applies to a sneaker box. It starts to matter around 20 lb, and by 35 to 50 lb in a padded double box it usually decides the carrier for you.
Three heavy items, priced on one day
Each item was packed the way it should travel, in a second box with padding around the first, and quoted with a real street address at both ends. Every service the engine returned is listed.
A vintage stereo receiver, Chicago to Los Angeles
24 x 20 x 12 in is 5,760 cubic inches, so the box bills as 42 lb against a real weight of 40 lb.
| Carrier | Service | Price | Quoted window |
|---|---|---|---|
| FedEx | Home Delivery | $45.86 | no window returned with this rate |
| UPS | Ground | $50.13 | no window returned with this rate |
| FedEx | Express Saver | $146.61 | 4-5 business days |
| USPS | Ground Advantage | $159.24 | 4-5 business days |
| USPS | Priority Mail | $198.99 | 3-4 business days |
A home espresso machine, Atlanta to Denver
20 x 18 x 18 in is 6,480 cubic inches, so the box bills as 47 lb, twelve more than it weighs.
| Carrier | Service | Price | Quoted window |
|---|---|---|---|
| FedEx | Ground | $35.40 | 4-5 business days |
| UPS | Ground | $42.38 | no window returned with this rate |
| UPS | 3 Day Select | $90.96 | 3-4 business days |
| FedEx | Express Saver | $109.15 | 3-4 business days |
| USPS | Ground Advantage | $146.49 | 4-5 business days |
A tube guitar combo amplifier, Philadelphia to Dallas
30 x 24 x 14 in is 10,080 cubic inches, so the box bills as 73 lb against a real weight of 48 lb.
| Carrier | Service | Price | Quoted window |
|---|---|---|---|
| UPS | Ground | $79.57 | no window returned with this rate |
| FedEx | Ground | $87.53 | 5-6 business days |
| FedEx | Home Delivery | $170.48 | 4-5 business days |
| USPS | Ground Advantage | $184.84 | 4-5 business days |
| USPS | Priority Mail | $229.09 | 3-4 business days |
The cheapest ground row came in at $45.86, $35.40 and $79.57; USPS Ground Advantage asked $159.24, $146.49 and $184.84 for the same boxes. Two of the destinations were priced to a business street, where FedEx quotes Ground; to a house it quotes Home Delivery, which can cost a little more. Quote your own box and both real addresses before you agree on anything with the buyer.
Before you agree on shipping with the buyer
- Get paid in full firstPayment cleared in your own account before the box is sealed. A buyer who will not pay until it ships is the oldest local-sale scam there is; the craigslist guide walks through the order.
- Pack it twiceThe item wrapped and boxed, then that box floated in a second carton with two to three inches of padding on every side. Vintage gear rarely breaks in the truck; it breaks in a single box with loose peanuts.
- Weigh and measure the packed box, then round upThe outer carton is what the carrier measures. A box that grows by two inches in each direction can add ten billable pounds.
- Quote it with both street addressesSome ground services only price a heavy box against a real street on each end, so a ZIP-only estimate can miss the cheapest row.
- Declare the real value on the labelUPS and FedEx cover only 100 dollars by default. For a receiver or an espresso machine worth several hundred dollars, declare what it is worth and keep the sale record.
- Photograph it, then send the tracking numberA photo of the packed box and the label is your record if anything arrives bent. Nobody else will send the buyer the tracking number for you.
Big boxes pay for air
The espresso machine weighs 35 lb but bills as 47. Trimming an inch off each side of the outer carton is often worth more than any carrier comparison.
One sale, no account
Somebody shipping a single amplifier does not need a carrier account or a monthly plan. Describe it, enter both addresses, pay and print as a guest.
Past 150 lb it is freight
A pair of floor-standing horns or a full cabinet is usually past what a parcel carrier takes. That is a pickup job or freight, not a label, and we sell parcel labels only.
Heavy local-sale questions
Is USPS cheaper for a 40 lb package?
Usually not once the box is big. On 2026-10-17 a 24 x 20 x 12 in carton at 40 lb from Chicago to Los Angeles quoted $45.86 by FedEx Home Delivery and $159.24 by USPS Ground Advantage. Bulky boxes are billed by size, and USPS adds a nonstandard fee above two cubic feet.
What is the heaviest box I can ship as a parcel?
USPS takes up to 70 lb and 130 inches in length plus girth. UPS and FedEx take up to 150 lb and 165 inches. Past that it is freight, which is a different product with a different booking process.
Do I need a carrier account to ship one heavy item?
No. Describe the packed item, enter both addresses, compare the rates and pay as a guest. The label comes with tracking, which you send to the buyer yourself.
How do I protect an expensive item in transit?
Pack it in two boxes with two to three inches of padding between them, photograph it packed, and declare its real value on the label. UPS and FedEx cover only 100 dollars by default, which is far below what a vintage amplifier is worth.