USPS Shipping Calculator

Get the best USPS shipping rates with ShipStation. Use our simple USPS shipping calculator to calculate your savings on label fees!

Access Low USPS Shipping Rates & More

ShipStation & USPS

Depending on your package’s size, weight, and destination, some options may be more affordable than others. To learn more about these services as well as others offered by the USPS, read our breakdown of USPS services.

USPS First Class Mail

USPS First Class Mail is an economical way to ship parcels, thick envelopes, and envelopes weighing under 16 oz. Packages must be smaller than the maximum dimensions of 22″ x 18″ x 15″. Delivery usually takes 3-4 business days to reach its final destination.

USPS Priority Mail

USPS Priority Mail is a great option to send parcels weighing less than 70 lbs domestically. They may not exceed 108” in combined length and girth (the length of the longest side, plus the distance around the thickest part of the package). Generally, USPS Priority Mail takes 1-3 business days to reach its final destination.

USPS Priority Mail Express

USPS Priority Mail Express has the same size and weight restrictions as standard Priority Mail. However, the delivery timeframe is either next-day or 2-day between pickup and final delivery.

USPS Parcel Select

USPS Parcel Select is an economical way to ship bulk parcels. Packages can weigh up to 70 lbs. and they can measure up to 130” in combined length and distance around the thickest part. These parcels have a wide range in delivery times and can take 2-8 days to reach their final destination.

Competitive USPS Shipping Rates

ShipStation offers these discounted rates because of our close relationship with USPS postage provider Our rates are far lower than you would receive at the post office directly. But ShipStation doesn’t just offer cheap shipping rates, we also offer efficiency and shipping automation tools that save you hours each day on shipping. Once you’ve packed all your orders and printed the labels, you can skip the line drop the labels off at a carrier facility, or schedule a pickup.

ShipStation and offer you some of the lowest USPS shipping rates you will find anywhere. There’s no shipping volume you have to reach to access these rates. You access these rates simply by shipping with ShipStation. To see how much time and money you can save on your ecommerce shipping, sign up now for a 30-day free trial.


Does USPS charge by weight or by size?

The USPS charges by both weight and package size. While there are generally weight thresholds that determine rates, there are more factors to be aware of. If packages are small but heavy, they may receive cubic pricing discounts. Conversely, if a package is lightweight but large, dimensional weight may increase the rates. For a full breakdown of ShipStation’s USPS rates, read our guide to USPS rates.

How are USPS shipping costs calculated?

Shipping rates are determined by package a package’s weight, dimensions, rate tier, and the distance between the ship-from and ship-to location (referred to as a zone).

What is the biggest box that I can ship with USPS?

The maximum allowable size for many mailpieces is 108” in combined length and girth (the distance around the thickest part of a package). USPS Retail Ground can measure up to 130” in combined length and girth, but this is subject to oversized pricing. Regardless, the heaviest a Priority Mail parcel may weigh is 70 lbs.

Start Saving on postage by trying ShipStation for free for 30 days!