Short answer: For most small, light packages (under about 2 lbs), USPS Ground Advantage is the cheapest way to ship. For something heavy but compact, a USPS Priority Mail Flat Rate box often wins. Once a package gets large or heavy (roughly 20 lbs or more), or is traveling a long distance, UPS Ground or FedEx Ground usually beat USPS. And whatever you send, buying the postage online instead of at the counter saves you 15% or more automatically.
There is no single cheapest carrier for everything. The winner changes with the package’s weight, its size, how far it is going, and how fast it needs to arrive. Here is how to find the lowest price every time.
The quick rule: cheapest carrier by package
| Your package | Usually cheapest |
|---|---|
| Small and light (under ~2 lbs) | USPS Ground Advantage |
| Heavy but small enough to fit a flat rate box | USPS Priority Mail Flat Rate box |
| Medium weight (5 to 20 lbs), shorter distance | USPS Ground Advantage |
| Medium weight, long distance | Compare UPS Ground and FedEx Ground |
| Large or heavy (20+ lbs) | UPS Ground or FedEx Ground |
The pattern is simple: USPS owns the small-and-light end, the private carriers own the big-and-heavy end, and the middle is a coin toss you settle by comparing quotes.
USPS: cheapest for small and light
For the majority of everyday packages, USPS is the low-cost option. Ground Advantage is its workhorse service, covering packages up to 70 lbs, with tracking included and delivery in about 2 to 5 business days. It starts around $5.50 when you buy postage online (roughly $7.90 at the counter) for the smallest, lightest parcels and scales up from there by weight and distance.
When your item is heavy for its size, a Priority Mail Flat Rate box can be the cheapest choice of all, because you pay one price no matter the weight (up to 70 lbs) or distance. Current Post Office flat rate prices are:
| Flat Rate option | Price |
|---|---|
| Flat Rate Envelope | $12.90 |
| Small Flat Rate Box | $13.65 |
| Medium Flat Rate Box | $24.80 |
| Large Flat Rate Box | $34.00 |
Flat rate is worth it whenever your item is dense, like a stack of books or a set of tools, and fits in the box. If it is light and roomy, weight-based Ground Advantage is usually cheaper. For a deeper breakdown of USPS pricing, see our guide on the cost to ship a package with USPS.
UPS and FedEx: cheaper for heavy or bulky
Once a package passes about 20 lbs, or is physically large, UPS Ground and FedEx Ground (Home Delivery to residences) generally undercut USPS, especially over longer distances where USPS zone pricing climbs steeply. The two are close on price, so the honest advice is to get a quote from both for your exact package. In the common comparisons people search for, USPS wins small, UPS and FedEx win big, and for a mid-size box it genuinely depends on the weight and the zones, which is why comparing beats guessing.
The biggest money-saver: buy postage online
This is the single easiest way to pay less, and most people miss it. Every carrier charges a lower “commercial” rate when you buy a label online instead of at the counter. For USPS that is the difference between counter (retail) pricing and the cheaper online price, typically 15% to 30% less, and there is no account, subscription, or minimum volume required. You can buy USPS labels through Click-N-Ship, and third-party shipping platforms offer discounted USPS, UPS, and FedEx labels in one place. If you ship even occasionally, printing your own label at home is almost always cheaper than standing in line.
Watch out for dimensional weight
Carriers charge by “dimensional weight” when a box is large but light, meaning you can be billed for the space the box takes up rather than what it actually weighs. The fix is to right-size your packaging: use the smallest box that fits, and for soft or flexible items, a padded mailer instead of a box can cut the cost substantially. Our guide to the best poly mailers for clothing is a good example of swapping a bulky box for lighter packaging.
Cheapest option, scenario by scenario
- A paperback book or small gift (under 1 lb): USPS Ground Advantage, bought online.
- A heavy, compact item like tools or canned goods: USPS Small or Medium Flat Rate box.
- A folded clothing order: USPS Ground Advantage in a poly mailer, not a box.
- A 25 lb box across the country: Compare UPS Ground and FedEx Ground; one will usually beat USPS.
- A large, light item (a lampshade, a pillow): Right-size the box first, then compare carriers, because dimensional weight will drive the price.
The bottom line
The cheapest way to ship a package is to match the carrier to the package, not to loyally use one for everything. Reach for USPS Ground Advantage for small and light, a flat rate box for heavy and compact, and UPS or FedEx Ground for large and heavy or long distance. Then take the two steps almost everyone forgets: buy the label online for the commercial rate, and right-size your box to dodge dimensional-weight charges. Do that and you are paying the lowest realistic price on every shipment. You can check the current cheapest USPS service on the official USPS Ground Advantage page.
