USPS Flat Rate Boxes, Prices and Sizes & WooCommerce Shipping

USPS flat rate boxes have been the most used packing material in the US. These are just the boxes which cost you a fixed price as long as the parcel weighs less than 70 lbs. The boxes come in multiple sizes which makes them suitable for products of different sizes and weights. These are easily available and are economical packing materials. You can save up to 50% on your shipping expenses by using these boxes.

So let’s see the different flat rate boxes, their cost and USPS services which has this feature. We’ll also discuss how you can use these boxes while running your online store on WooCommerce.

Priority Mail Express & Priority Mail Flat Rate

Flat rate boxes are available with both Priority Mail Express and Priority Mail services from USPS. Priority Mail Express is a guaranteed delivery service which offers overnight scheduled delivery by 10:30 am. The Express service is available to most US addresses with a few exceptions. Flat rate for this service starts at $24.70 with 3 box types meant for different types of items. Whereas, Priority Mail is a standard delivery service by USPS. It usually delivers packages and envelopes in 1-3 days. The flat rate boxes for this service starts at $6.70 at the post offices. The commercial prices for the same starts at $6.55. The maximum allowed weight per box is 70 lbs. for both of the services.

You can get these boxes without any charges from USPS post offices near you or you can also order them online. In case you order them online, you get a free delivery to your address too. The shipping prices of these boxes are determined by the type of the boxes and not their weights. For instance, the large flat rate box and the small flat rate box will cost you $17.65 and $7.05 respectively, and you can still ship products up to 70 lbs. in them.

USPS Flat Rate Boxes

Flat rate boxes are available with USPS Priority Mail Express and Priority Mail services. USPS offers two types of pricing for these boxes. One is the Post Office Rates and the second is the Commercial Rates. Commercial rates are slightly lesser than the post office rates, but you require a minimum of 50 parcels for the commercial pricing by USPS. Alternatively, you can go for and EasyPost for commercial and discounted rates of these boxes. The boxes are:

  • Priority Mail Express Flat Rate Envelope
  • Priority Mail Express Legal Flat Rate Envelope
  • Priority Mail Express Flat Rate Box
  • Priority Mail Express Padded Flat Rate Envelope
  • Priority Mail Flat Rate Envelope
  • Priority Mail Flat Rate Medium Box
  • Priority Mail Flat Rate Large Box
  • Priority Mail Flat Rate Small Box
  • Priority Mail Padded Flat Rate Envelope
  • Priority Mail Gift Card Flat Rate Envelope
  • Priority Mail Window Flat Rate Envelope
  • Priority Mail Small Flat Rate Envelope
  • Priority Mail Legal Flat Rate Envelope

Post Office and the Commercial Rate Sheet for USPS Flat Rate Boxes

Name of the BoxSize/DimensionPost Office RatesCommercial Rates
Priority Mail® Express
Flat Rate Envelope
Padded Flat Rate Envelope*
Legal Flat Rate Envelope
12-1/2″ x 9-1/2″
12-1/2″ x 9-1/2″
15″ x 9-1/2″
Priority Mail®
Flat Rate Envelope12-1/2″ x 9-1/2″ or smaller$6.70$6.55
Legal Flat Rate Envelope*15″ x 9-1/2″$7.00$6.85
Padded Flat Rate Envelope*12-1/2″ x 9-1/2″$7.25$7.10
Small Flat Rate Box8-5/8″ x 5-3/8″ x 1-5/8″ In
8-11/16″ x 5-7/16″ x 1-3/4″ Out
Medium Flat Rate Box
Top Loading
11″ x 8-1/2″ x 5-1/2″ In
11-1/4″ x 8-3/4″ x 6″ Out
Medium Flat Rate Box
Side Loading
13-5/8″ x 11-7/8″ x 3-3/8″ In
14″ x 12″ x 3-1/2″ Out
Large Flat Rate Box12″ x 12″ x 5-1/2″ In
12-1/4″ x 12-1/4″ x 6″ Out
APO/FPO Large Box12″ x 12″ x 5-1/2″ In
12-1/4″ x 12-1/4″ x 6″ Out


Large Flat Rate Box with inner dimensions 23-11/16″ x 11-3/4″ x 3″ and outer dimensions 24-1/16″ x 11-7/8″ x 3-1/8″ is available with only.

*Packaging only available at

How to get USPS Flat Rate Boxes?

These flat rate boxes help you in multiple ways. First, you get them without paying a fee. And second, these are made up of strong material and have the name of the service written on them. So you save money in two different ways. This adds to the ways you can cut your expenses on shipping. Finally, you get these delivered this to your address when you order them online.

You can get these boxes from your nearest post office for free. Or you can order them online. To do that you’ll require a USPS account. This will be a regular USPS account. You can sign up here for a USPS Account. For discounted postage rates and printing labels, you can go for the e-VS account which is subject to your previous shipment volumes. An EasyPost account gives you an automatic USPS account with the access to discount pricing. So even if you don’t open a USPS account directly, you can use these credentials to order USPS Flat Rate boxes.

EasyPost vs Priority Mail® Flat Rate Box Charges

EasyPost and are two of the premiere online vendors of USPS Postage. These technology-based companies provide an economical and convenient way of printing USPS postage paid shipping labels. is limited to USPS services whereas EasyPost helps customers integrate with more than 110 carriers. The service that suits you best, may depend upon your monthly shipment volume when using USPS services. This is because they differ in the extra service charge. If we make a general comparison, EasyPost is better for small and medium-sized businesses based on extra charges. becomes economically beneficial as the number of shipment grows. In such situations, you can contact for an enterprise account and get an exclusive pricing plan.

Talking about the Flat Rate boxes, both services offer discounted rates. Here is a table comparison.

Flat Rate Box Rates Offered by EasyPost and Respectively

BOX NAMEEasyPost Rates
Flat Rate Options$6.35$6.55
Legal Flat Rate Envelope$6.65$6.85
Padded Flat Rate Envelope$6.90$7.10
Small Flat Rate Box$6.85$7.05
Medium Flat Rate Box
– Top Loading
Medium Flat Rate Box
– Side Loading
Large Flat Rate Box$17.10$17.65
APO/FPO Large Box$16.15


Advantages of EasyPost

Lesser Rates– As you can see, EasyPost offers these boxes at a price 25¢ -45¢ lesser than on each box.

Higher Number of Carriers– EasyPost helps a user to integrate with more than 110 carriers, whereas works for USPS only.

Good for Small and Medium Scale Businesses– EasyPost charges you 1¢ per package on a ‘pay as you go’ basis, which means you can start printing labels and pay at the same time. charges $15.99 per month. So, doing the simple maths you are good to go with EasyPost till you ship 1599 or more packages in a month.

So a lesser rate, higher number of supported carriers, and great usability for small and medium businesses make EasyPost a preferable option.

USPS Flat Rate Boxes with WooCommerce Shipping Plugins

And finally, WooCommerce store owners can integrate USPS services with the additional ‘Flat Rate Boxes’ option through extensions. The three plugins built by ELEX that help you do so are listed below. You can enable ‘Flat Rate Boxes’ by selecting the boxes you want to offer to your customer. We’ll see how to enable and select boxes for each of these plugins separately.

WooCommerce USPS Shipping Plugin with Print Label

You can enable USPS flat rate as you navigate to your Dashboard> WooCoommerce> Settings> Shipping> USPS> Rates & Service> Flat Rate and choose ‘Yes – Enable flat rate services’.

usps flat rate boxes in WooCommerce usps shipping plugin with print label

The Flat Rate sections include the following options:

  • Boxes & envelopes
    • Yes – Enable Flat Rate Service– Select this option to enable flat rate service on the cart/checkout page.
    • No – Disable Flat Rate Services– Select this option to disable this service.
    • Enable Priority Flat Rate Services Only– If you want to offer only Priority Flat Rate service select this option.
    • Enable Express Flat Rate Services Only– If you want only Priority Express Flat Rate services, select this option.
  • Flat Rate Boxes- You will require to click in the box given to see all the flat rate boxes. Click on any of the boxes to add.
  • Custom Names- You can give custom names for these boxes. It remains the Priority Mail Express Flat Rate and Priority Mail Flat Rate by default.
  • Flat Rate Fee-  You can add a per box fee here in $ or % of the rate per box. This is added to the actual rate of the box.

Enabling this will help you print labels for each flat rate box from the admin panel of your WooCommerce store. If you are new to the WooCommerce environment here is how you generate USPS postage paid labels from within WooCommerce.

EasyPost Shipping Method Plugin for WooCommerce

You can enable USPS flat rate as you navigate to your Dashboard> WooCoommerce> Settings> Shipping> EasyPost> Rates & Service> Flat Rate Boxes and click on the box to get the list of flat rate boxes available. You also get the option to add an additional ‘Flat Rate Fee’.

The plugin lists the USPS Flat Rate Boxes with different names. Here is a list of real names and the names used by EasyPost.

  • Letter Envelope– Flat Rate Envelope
  • Gift Card Envelopes– Flat Rate Gift Card Envelope
  • Window Envelopes– Flat Rate Window Envelope
  • Small Envelopes– Small Flat Rate Envelope
  • Padded Envelopes– Flat Rate Padded Envelope
  • Legal Envelopes– Flat Rate Legal Envelope
  • Small Box– Small FlatRate Box
  • Medium Boxes– Medium Flat Rate Box
  • Large Box– Large Flat Rate Box Shipping Plugin with USPS Postage for WooCommerce

In Shipping Plugin you can enable USPS flat rate as you navigate to your Dashboard> WooCoommerce> Settings> Shipping>> Rates & Service>  and check the box against the service you want to activate. You also get an option where you can prioritize the flat rates over other services. You can print shipping labels for these boxes from the edit order page. Refer the setup guide for the complete guide on USPS label generation.

Enabling Flat Rate Boxes in Shipping Plugin with Print Label for WooCommerce


So if you are having a WooCommerce store or planning to have one, you have all the options to integrate it with USPS. With the above-listed plugins, you can enable USPS Flat Rate Boxes with a click. Our EasyPost and integrations help you take benefits of the discounted prices from USPS at a nominal charge. Our USPS integration for WooCommerce is enabled with the recently introduced e-VS services by USPS. You require a minimum of 50 parcels per week for its discounted pricing. This restriction is not there with and EasyPost.

With three options to add USPS Flat Rate Boxes to your WooCommerce store, you can save up to 50% on your shipping expenses. Discounted rates and free supplies give you a better experience in managing your shipping budget. If you are not using USPS service, its time to switch for a cheaper alternative. Visit our product page for plugin details and contact our dedicated online support for any technical issue or pre-sales queries.

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