Shipping used goods without losing money

Pirate Ship: the tool most casual sellers don't know about

Before any of the rules below, the single biggest cost lever a casual seller can pull: stop buying labels at retail prices. USPS retail rates (the ones you see at a post-office counter or on the eBay-Mercari-Poshmark default flow) are higher than the commercial rates that high-volume shippers pay. The gap is real, and there's a free service that closes it for everyone: Pirate Ship (pirateship.com).

Pirate Ship hands out USPS commercial-rate labels with no monthly fee, no minimum volume, and no marketplace lock-in. As of April 2026, the typical savings vs. USPS retail run roughly 10% to 30% per label depending on weight and service, with the bigger gaps on Ground Advantage and Priority. The site looks unserious; the rates are real. UPS labels through their integration are similarly discounted relative to UPS daily rates.

For a casual seller moving five to fifty packages a year, this is the single largest cost reduction available without changing anything else. The marketplace-default labels are convenient; they're not the cheapest. If your sale isn't locked into a marketplace's built-in shipping flow, paste the address into Pirate Ship and pay the commercial rate.

The three ways most sellers lose money on shipping

The pattern is consistent. Sellers offer "free shipping" they never priced into the listing. Sellers pick the wrong service for the item shape and pay more than they had to. Sellers skip insurance on something fragile and eat the loss when it breaks. None of these have a one-size-fits-all fix. A two-pound book and a thirty-pound floor lamp are different shipments; a cast-iron pan and a glass vase are different risk profiles.

What follows are general guidelines, not hard rules. The specifics will move with the item, the destination, and the value at stake.

Packaging the carriers already give you

The boring trick most sellers don't use: the carriers will hand you the boxes for free if you're using their service. USPS Priority boxes are free to order through usps.com and delivered to your door at no charge. UPS and FedEx have free packaging for their own services as well. Carriers will deliver bulk packaging to a residential address; you do not have to be a business.

Beyond carrier-provided packaging: reused Amazon and other delivery boxes (almost-free supply, just remove the old labels with a marker or a fresh address sticker), grocery-store paper for fill, used bubble wrap saved from your own deliveries. The packaging cost on most items can run close to zero if you're willing to keep a small box of supplies.

Flat-rate vs. calculated: pick by item shape, not item value

Calculated shipping (priced by weight plus distance) wins for most items because it scales with the actual cost. The buyer pays whatever it costs to ship to them; you don't have to guess. Flat-rate wins for a narrow band: heavy items in small boxes, where the actual weight would push calculated rates above the flat-rate price.

Rough rule: if your item is heavier than about 5 lbs and fits in a flat-rate box, run both rates side by side. Otherwise default to calculated. Sellers who use flat-rate for everything (especially light items in big boxes) routinely overpay by a few dollars per package, and that adds up over a year.

The dimensional-weight gotcha

UPS and FedEx don't always charge by what your package weighs. For boxes that are big-but-light, both carriers calculate a "dimensional weight" (length times width times height divided by 139 for ground service in the US, as of April 2026), then bill on whichever number is higher: actual weight or dimensional weight. The math catches sellers off guard on items like pillows, lampshades, or anything packed in an oversized box.

Practical rule: if your item is light but the box is large, measure the outside dimensions and run the dimensional-weight math before you pick a carrier. USPS Ground Advantage and Priority Mail use dimensional weight only above 1 cubic foot, so for boxes under that threshold USPS often wins on light-but-bulky items. Above 1 cubic foot, UPS and FedEx will both apply the dimensional charge regardless. Knowing which side of the threshold your package sits on changes the cheapest carrier.

The free $100 insurance most sellers forget about

USPS Priority Mail includes $100 of declared-value coverage at no extra charge. UPS Ground includes $100 of declared-value coverage at no extra charge. Both have been baseline features for years; neither carrier markets them aggressively, and most sellers don't realize the coverage is already there.

That free $100 baseline is the entire reason the "under $100, skip the insurance" rule of thumb works. The insurance isn't skipped; it's already included in the rate. Above $100, additional declared-value coverage runs roughly $1.65 to $3.05 per $100 of value depending on carrier and service class, and at that point the math becomes a per-shipment decision.

Heavy, fragile, awkward: when to charge, when to refuse

Some items eat your profit if you're not careful with them. Heavy items where shipping cost approaches half the sale price. Fragile items where insurance becomes mandatory. Awkwardly shaped items that don't fit standard boxes: lamps, framed art, sports equipment, anything with one long dimension.

Two answers depending on the math:

• Charge correctly. If shipping is going to cost $30, the buyer pays $30. Don't bury it in the item price; calculated shipping does this automatically and the buyer sees the real number before they commit.
• Local pickup only. For items where shipping would exceed about a quarter of the sale price, "pickup only" in your local marketplace listing is often the right call. Less reach, but no shipping disaster on the back end.

Some items just shouldn't ship. A 50-pound piece of exercise equipment, a tall floor lamp with a fragile shade, an oversized framed print: the right marketplace for these is local. Knowing which items belong in that category saves you from one bad return that wipes out a month of small wins.

The recap, as a numbered list

1. Use Pirate Ship for any label not locked into a marketplace flow. Commercial rates, free service.
2. Order free Priority and UPS boxes from the carriers; never pay for packaging that the carrier hands out.
3. Default to calculated shipping. Use flat-rate only for heavy items in small boxes.
4. For light-but-large items, run dimensional weight before picking UPS or FedEx; USPS often wins under 1 cubic foot.
5. Trust the free $100 insurance baseline on Priority and UPS Ground. Pay for additional coverage only above $100.
6. Items that approach a quarter of the sale price in shipping cost should be pickup-only or priced for it.
7. Self-insure under $100, paid-insure over it. The threshold is regret, not math.

For the side of shipping that's about what you can't legally put in a box (hazmat, lithium batteries, restricted categories), the next read is what you can't (or shouldn't) sell online.