The cheapest way to ship a package with USPS.

Ask which USPS service is cheapest and the honest answer is: it depends on the package. USPS prices most packages by weight and zone (how far it's going), and size can add to that. How fast it has to arrive matters too. The good news: there are only a few services to compare, and a few habits that keep postage down.

The USPS services to compare

• USPS Ground Advantage: packages up to 70 lb, delivered in 2–5 days, with USPS Tracking included. Packages under a pound are priced in ounce steps (up to 4, 8, 12 and 15.999 oz). Heavier packages are priced by the pound, rounded up. For most packages that aren't urgent, this is the first one to check.
• Priority Mail: 2–3 days, up to 70 lb, with tracking included. In your own box it's priced by weight and zone. USPS says Priority Mail has no surcharges for fuel, residential or rural delivery, or Saturday delivery.
• Priority Mail Flat Rate: USPS boxes and envelopes with one price for any weight up to 70 lb, going to any state. The packaging is free.
• Priority Mail Express: the fastest service, 1–3 days with a money-back guarantee. It costs more than Priority Mail, so save it for orders where the date really matters.
• Media Mail: 2–8 days, only for eligible media such as books (at least 8 pages), CDs and DVDs, and printed music. Video games and computer drives don't qualify, and USPS can open any Media Mail package to check. If something ineligible is inside, you or your buyer pay the higher postage.

Light, flat items that bend easily can go as First-Class Mail large envelopes (up to 13 oz). Anything thicker or rigid is a package.

Buy online, not at the counter

USPS charges less for postage bought online. Its own service pages say that shipping online gets lower Commercial prices than the Post Office counter for Priority Mail Express, Priority Mail and Ground Advantage. Shipping apps buy postage online too. In Muvo, every rate shows next to the retail price, so you can see the difference before you buy.

When Flat Rate is worth checking

Flat Rate pricing ignores weight and distance. That makes it worth comparing when an item is small, heavy and going far. For a light item going nearby, a weight-and-zone price is often lower. Two rules to know: the box flaps must close within the normal folds, and Flat Rate packaging is exempt from USPS nonstandard fees.

Cubic pricing for small, heavy parcels

Commercial Priority Mail and Ground Advantage also have cubic pricing, where the price is set by the package's size tier instead of its weight. Pieces must weigh 20 lb or less, with the longest side no more than 22 inches. The size limit is 0.5 cubic foot for Priority Mail cubic and 1 cubic foot for Ground Advantage cubic. Rolls and tubes don't qualify. Whether you see cubic prices depends on the tool you buy postage with.

Habits that lower USPS postage

1. Weigh every package. Postage rounds up to the next price step, so a few ounces can move a package into a higher one.
2. Use the smallest box that protects the item. Packages larger than 1 cubic foot can be charged by dimensional weight. See dimensional weight, explained.
3. Watch long boxes. USPS adds nonstandard fees for packages longer than 22 inches, longer than 30 inches, or bigger than 2 cubic feet.
4. Enter real dimensions. USPS charges a dimension-noncompliance fee when dimensions are missing or wrong and dimensional weight applies.
5. Compare at the moment you buy. The cheapest service changes with each package and address. Check Ground Advantage, Priority Mail and Flat Rate every time, not just once.
6. Don't pay for speed you don't need. If your store promises 3–5 days, a faster service is a cost, not a feature.

Let Muvo compare for you

In Muvo you save a box and weight for each product once. When an order comes in, Muvo builds the package, checks the address, compares USPS and UPS rates and picks the cheapest qualifying one. You can switch between Cheapest, Best value and Fastest, or pick any rate by hand, and every price shows before you buy.

Muvo has no monthly fee on the Free plan. See pricing for the label fee and what Pro adds, or create a free account and connect your store.

Sources: USPS, USPS Ground Advantage, Priority Mail and Mail & Shipping Services; USPS Domestic Mail Manual 223 (Priority Mail Commercial) and 283 (Ground Advantage Commercial). USPS rules change, so check usps.com before you rely on a detail.