USPS Shipping Rates: How Prices Work by Weight and Zone

USPS shipping rates are set by five things: the service (Ground Advantage, Priority Mail, Priority Mail Express, Media Mail or Flat Rate), the package’s billable weight, the zone between the origin and destination ZIP Codes, the package size, and whether you pay retail prices at the counter or lower commercial prices online. USPS publishes every rate in its Notice 123 price list, and the current edition took effect October 4, 2026.

Prices change more than once a year, so this guide explains how USPS rates are built, which service fits each kind of package, and how to pay commercial prices instead of retail. For the exact price of your package today, compare live USPS and UPS rates in the ParcelPath rate calculator.

How are USPS shipping rates calculated?

Every USPS package price comes from a grid of weight rows and zone columns for one service. You find the row for the package’s billable weight, the column for its zone, and then add any extra services or size-based fees. Our step-by-step guide to calculating USPS shipping rates walks through a full example.

• Service: faster services cost more at the same weight and zone.
• Weight: USPS rounds any fraction up to the next pricing tier.
• Zone: zones run from Zone 1 (local) to Zone 9, based on the distance between ZIP Codes. Our USPS zone map shows how they’re drawn.
• Size: large boxes can be billed on dimensional weight, and long or bulky ones add nonstandard fees.
• Price type: commercial prices, available when you buy postage online, are lower than retail counter prices.

How do USPS shipping rates change by weight?

Each service uses its own weight tiers in Notice 123. Knowing where the tier breaks fall is the easiest way to avoid paying for an extra ounce or pound you don’t need.

The practical lessons: on Ground Advantage, a 15-ounce package is priced in the 15.999-ounce tier, below the 1-pound row, so trimming packaging to stay under a pound can make a real difference. On Priority Mail, a 2.1-pound package is billed as 3 pounds. Flat Rate breaks the weight link entirely, which is why it can win for heavy items. Our guide to the cost to ship a bubble mailer with USPS shows how light mailers fall into these tiers.

Which USPS service has the right rate for your package?

The service sets the price ladder before weight and zone do. The table below compares the domestic package services by delivery time, size limit and best use.

USPS Ground Advantage is the lowest-cost choice for most parcels and replaced First-Class Package Service, Retail Ground and Parcel Select Ground in July 2023. Priority Mail adds speed and free boxes, and our comparison of Priority Mail vs Ground Advantage shows when the upgrade is worth it.

Priority Mail Express is the only domestic USPS package service with a money-back guarantee, and our guide to Priority Mail Express cost covers ways to save on it. Media Mail is restricted to eligible educational media and may be inspected, so don’t use it for general merchandise.

When are USPS Flat Rate prices cheaper than weight-based rates?

Priority Mail Flat Rate charges one price for each box or envelope to any U.S. address, for contents up to 70 pounds. That makes it strongest for small, heavy items going far, such as tools, hardware or books shipped cross-country. For light packages or short distances, weight-based Ground Advantage or Priority Mail is usually cheaper.

The box’s flaps must close within their normal folds, so overstuffed boxes don’t qualify. Our walkthrough of how much it costs to ship a Medium Flat Rate Box shows how to compare it with a weight-based label.

How does package size affect USPS rates?

Size can matter as much as weight. For Priority Mail and Ground Advantage packages larger than 1 cubic foot (1,728 cubic inches), USPS calculates dimensional weight: multiply length × width × height in inches, rounding fractions up, and divide by 139. If that number is higher than the actual weight, you pay the dimensional weight price.

USPS adopted the 139 divisor in July 2026, replacing the older 166, so many calculators and guides that still use 166 understate the billable weight. Nonstandard fees also apply to packages longer than 22 inches, longer than 30 inches, larger than 2 cubic feet (3,456 cubic inches), or in unusual shapes such as tubes and rolls. A box that’s a few inches smaller can avoid both.

What are USPS rates for letters and stamps?

Letters and large envelopes go by First-Class Mail, not a package service. A letter can weigh up to 3.5 ounces and a large envelope (flat) up to 13 ounces, and anything thicker, rigid or lumpy is priced as a package instead. Our guide to how heavy a letter can be for a First-Class stamp explains the limits.

For larger envelopes, our chart of how many stamps you need for a large envelope converts weight into stamp counts, and Forever stamps never expire, so they keep their value after a price change. If you need proof of mailing and delivery, you can send the letter by Certified Mail, and our breakdown of Certified Mail cost lists the add-ons. See USPS First-Class Mail for the official rules.

What international shipping rates does USPS offer?

USPS international prices depend on the service, the weight and the destination’s price group. The main options are Priority Mail International (6–10 business days), Priority Mail Express International (3–5 business days to many countries) and First-Class Package International Service for packages up to 4 pounds. Global Express Guaranteed has been suspended since September 29, 2024.

Service to some countries is limited or suspended, so check USPS’s international service alerts before promising a delivery date. Every international package also needs a customs form, which online labels fill in for you.

How do you pay less than USPS retail rates?

USPS charges two main price levels. Retail prices apply when you pay at the Post Office counter. Commercial prices apply when you buy postage online, through USPS Click-N-Ship or an approved online postage provider, and they’re lower for Priority Mail, Priority Mail Express and Ground Advantage. Larger shippers can qualify for deeper contract pricing.

ParcelPath is one way to get there for free: no subscription, no per-label fee, no minimums and no contract, with up to 89% off USPS retail rates and up to 85% off UPS. ParcelPath also offers free USPS pickups and USPS Label Broker, so you can show a code at the Post Office instead of printing a label. Our guides to the USPS shipping discount and USPS discounts explain how the savings work.

To price a specific package before you buy, try the USPS shipping rates calculator, read our USPS shipping calculator guide for tips on entering accurate weights and dimensions, or use the ParcelPath shipping calculator page to compare carriers side by side.

Frequently Asked Questions

Which USPS service has the lowest shipping rates?

USPS Ground Advantage has the lowest rates for most packages, with delivery in 2–5 business days and up to $100 of coverage included. The main exceptions are heavy items going far, where a Priority Mail Flat Rate box can be cheaper, and eligible books or media, where Media Mail costs less. Letters are cheapest with a First-Class stamp.

Does USPS charge by weight or by size?

Both. USPS prices packages by weight and zone, but for Priority Mail and Ground Advantage packages over 1 cubic foot it calculates dimensional weight (length × width × height ÷ 139) and charges whichever is higher. Packages longer than 22 inches or larger than 2 cubic feet also pay nonstandard fees.

How often do USPS shipping rates change?

USPS now changes shipping prices more than once a year, and each change goes to the Postal Regulatory Commission for review before it takes effect. In 2026, a major change took effect on July 12, including the switch to a 139 dimensional weight divisor, and the current Notice 123 price list is effective October 4, 2026.

Are USPS rates cheaper online than at the Post Office?

Yes. Buying postage online, through Click-N-Ship or an approved online postage provider, gets you USPS commercial prices, which are lower than the retail prices charged at the counter for Priority Mail, Priority Mail Express and Ground Advantage. Free platforms such as ParcelPath offer up to 89% off USPS retail rates.

Sources

• USPS Notice 123: Price List (effective October 4, 2026)
• USPS: USPS Ground Advantage (delivery time, 130-inch limit, dimensional weight, nonstandard fees)
• USPS: Priority Mail (delivery time, Flat Rate options, dimensional weight)
• USPS: Priority Mail Express
• USPS: Media Mail
• USPS Domestic Mail Manual 101: Physical Standards
• USPS: Click-N-Ship (commercial pricing online)
• USPS: Ship hub and Price Calculator