What Is USPS Flat-Rate Shipping and How Can I Use It?

Reducing the cost of postage and shipping is critical to increasing margins for an eCommerce business. If you aren't shipping your products the most efficient way or having a 3PL do that for you, you could be losing money for no reason. Understand USPS flat rate shipping here.

Reducing the cost of postage and shipping is critical to increasing margins for an eCommerce business. If you aren't shipping your products the most efficient way or having a 3PL do that for you, you could be losing money for no reason. One easy way to reduce your shipping cost is with USPS Flat Rate. With flat-rate shipping, the weight of your products isn't factored in. This is especially important for heavier items. It doesn't always make sense for lighter weight goods - something to consider. How do you know when to use USPS flat rate and when it does or doesn't make sense? We're going to try to help you decide. 


USPS Flat Rate shipping is just that — USPS branded packaging with flat postage rates, no matter how heavy the package is. If you're shipping heavy, small items, USPS Flat Rate can be one of the cheapest ways to ship, since the shipping cost remains the same regardless of the package weight or shipping distance. Keeping a supply of these boxes on hand for your fulfillment operations can cut your shipping costs by 50% annually.

USPS offers a variety of flat rate packaging options, including six sizes of envelopes and four types of boxes, to fit your unique shipping needs. All supplies are free of charge and can be picked up at your local Postal Office or mailed to you directly through USPS's website. Most shipping software supports flat rate packaging; you have to make sure you chose it when you're creating the label. 


It depends! We offer all of our clients our CPP pricing with USPS, which you can see here. It'll depend on the software/postage provider you're using as to how much it'll cost. 


Flat rate shipping is appealing for a few reasons based on how shipping costs are calculated, depending on the carrier. 

First, the farther the distance or zone you ship your orders to, the more expensive it typically is, and this only increases the heavier your order is. 

Additionally, dimensional weight is a commonly used pricing technique that is calculated by multiplying length times width times height of a package. Freight carriers like USPS, FedEx, and UPS calculate shipping charges based on whichever number is greater: the actual weight of the package or its calculated dimensional weight.

Flat rate shipping simplifies things and can be a great option, especially those who are smaller and self-fulfill orders.

Note: Flat rate shipping can also refer to a method for deciding how to price your shipping when you charge a flat or fixed shipping rate for every order (rather than offering free shipping or charging the real-time shipping rate at checkout). 


Flat rate shipping can create huge savings when it comes to shipping by having a lower, predictable cost. It doesn't make sense for every eCommerce business but is used most often by small business owners that pack boxes themselves and run to the post office to ship orders.

You can package anything up to 70 pounds

You don't have to worry about weighing and calculating shipping costs for each package. As long as the package is under the 70 lb. limit, then you can ship it with flat rate shipping all for the same cost. 

It's automatically insured up to $50 by USPS

Instead of you having to purchase shipping insurance separately, it's already taken care of. Every flat rate package is automatically insured up to $50. If the contents are worth $50 or less, your costs will be covered if lost. You have to file a claim with USPS. 

You can drop it off at any USPS store

When your package is ready to go, you can drop it off at any US Post Office to be shipped out. You can also schedule a pick up online if you have a lot of packages.

USPS tracking is included

You'll need this to send to your customer so they can track their package, and you can confirm delivery. You can enter the package number into USPS's tracker, and you can follow its progress until it's delivered.


You don't have to worry about weight with flat rate shipping, but that doesn't mean you can send anything. The following items are forbidden from being shipped through USPS:

  • Explosives
  • Firearm ammunition
  • Airbags
  • Alcohol
  • Gasoline
  • And more

Next article: USPS First Class Package and Other USPS Mail Classes

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