USPS flat rate boxes have been the most used packing material in the US. These are the boxes that cost a fixed price, as long as the parcel weighs less than 70 lbs. The boxes come in multiple sizes, making them suitable for products of varying 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
Priority Mail Express is a guaranteed delivery service that offers overnight scheduled delivery by 10:30 am. The Express service is available to most US addresses with a few exceptions. Priority Mail Express is now available based on weight and zone-based pricing. The post office price is $30.45, and the commercial rate is $29.25. 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 start at $6.70 at the post offices. The commercial prices for the same start at $11.70, and commercial pricing is at $10.60. 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 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 $29.95 and $11.70, respectively, and you can still ship products up to 70 lbs. in them.
USPS Flat Rate Boxes
Flat rate boxes are available with 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. Alternatively, you can go for Stamps.com and EasyPost for commercial and discounted rates for these boxes. The boxes are:
- Priority Mail Express Flat Rate Envelope
- Priority Mail Express Legal Flat Rate Envelope
- 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 Legal Flat Rate Envelope
Post Office and the Commercial Rate Sheet for USPS Flat Rate Boxes
| Name of the Box | Size/Dimension | Post Office Rates | Commercial 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″ |
$31.40 $33.25 $31.65 |
$27.20 0 The rate is not explicitly listed |
| Priority Mail® | |||
| Flat Rate Envelope | 12-1/2″ x 9-1/2″ or smaller | $11.00 | $9.70 |
| Legal Flat Rate Envelope* | 15″ x 9-1/2″ | $11.20 | $10.20 |
| Padded Flat Rate Envelope* | 12-1/2″ x 9-1/2″ | $11.95 | $10.50 |
| Small Flat Rate Box | 8-5/8″ x 5-3/8″ x 1-5/8″ In 8-11/16″ x 5-7/16″ x 1-3/4″ Out |
$11.70 | $10.60 |
| 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 |
$21.05 | $18.50 |
| 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 |
$21.05 | $18.50 |
| Large Flat Rate Box | 12″ x 12″ x 5-1/2″ In 12-1/4″ x 12-1/4″ x 6″ Out |
$29.95 | $27.10 |
| APO/FPO Large Box | 12″ x 12″ x 5-1/2″ In 12-1/4″ x 12-1/4″ x 6″ Out |
$28.70 | $25.85 |
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 USPS.com only.
*Packaging only available at USPS.com
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 to your address when you order them online.
Here’s how to get USPS flat rate boxes:
- Walk into the post office and pick up the USPS Priority Flat Rate Boxes free of cost
- Order from USPS.com with a free USPS account, and you will get it delivered free to your doorstep
- Through different shipping platforms like EasyPost or Stamps.com, and get access to discounted USPS shipping labels.
EasyPost vs Stamps.com- Priority Mail® Flat Rate Box Charges
EasyPost and Stamps.com are two of the premium online vendors of USPS Postage. These technology-based companies provide an economical and convenient way of printing USPS postage-paid shipping labels. Stamps.com is limited to USPS services, whereas EasyPost helps customers integrate with more than 110 carriers. The service that suits you best may depend on 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. Stamps.com becomes economically beneficial as the number of shipments grows. In such situations, you can contact Stamps.com 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 Stamps.com, Respectively
| BOX NAME | EasyPost Rates | Stamps.com Rates |
| Flat Rate Options | $8.40 | $7.99 |
| Legal Flat Rate Envelope | $8.70 | $8.29 |
| Padded Flat Rate Envelope | $9.10 | $8.79 |
| Small Flat Rate Box | $9.25 | $8.51 |
| Medium Flat Rate Box – Top Loading |
$17.50 | $14.38 |
| Medium Flat Rate Box – Side Loading |
$17.50 | $14.38 |
| Large Flat Rate Box | $24.30 | $19.51 |
| APO/FPO Large Box | $20.15 | $17.70 |
Key Observations:
- Stamps.com looks cheaper on some boxes, but can be availed at $15.99/month
- EasyPost offers transparent per-label pricing with no monthly cost, and works with more than 100 carriers
- The best choice depends on your shipment volume.
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.
- ELEX WooCommerce USPS Shipping Plugin with Print Label
- ReachShip Multi-Carrier & Conditional WooCommerce Shipping Plugin
- ELEX EasyPost Shipping Method Plugin for WooCommerce
-
ELEX Stamps.com Shipping Plugin with USPS Postage for WooCommerce
WooCommerce USPS Shipping Plugin with Print Label
You can enable USPS flat rate as you navigate to your Dashboard> WooCommerce> Settings> Shipping> USPS> Rates & Services
You can see the list of services
If you are new to the WooCommerce environment, here is how you generate USPS postage-paid labels from within WooCommerce.
ReachShip Multi-Carrier & Conditional WooCommerce Shipping Plugin
Once the plugin is downloaded, enter the ReachShip API credentials. Then, go to Settings and connect the carrier credentials to the plugin.
Learn more about how ReachShip works from their documentation.
EasyPost Shipping Method Plugin for WooCommerce
You can enable USPS flat rate as you navigate to your Dashboard> WooCommerce> Settings> Shipping> EasyPost> Rates & Services
To learn further about the EasyPost Shipping Plugin, check out the documentation.
Stamps.com Shipping Plugin with USPS Postage for WooCommerce
In the Stamps.com Shipping Plugin, you can enable USPS flat rate as you navigate to your Dashboard> WooCommerce> Settings> Shipping> Stamps.com> Rates & Services
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 to the setup guide for the complete guide on USPS label generation.
Conclusion
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 Stamps.com integrations help you take advantage 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.
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.
FAQs
- Are USPS Flat Rate Boxes free?
Yes. You can pick them up at your local Post Office or order them online for free. You only pay for postage. - What’s the difference between Post Office rates and Commercial rates?
Post Office rates are retail prices, while Commercial rates (via EasyPost, Stamps.com, etc.) are discounted online rates. - Do EasyPost and Stamps.com offer the same USPS discounts?
Both provide Commercial Pricing, but EasyPost uses a pay-per-label model, while Stamps.com charges a monthly fee. - Can I ship anything in a USPS Flat Rate Box?
You can ship most items, but hazardous materials and prohibited items are not allowed. - Which Flat Rate Box is the cheapest?
The Priority Mail® Small Flat Rate Box is the most affordable option, starting at around $8.51 (Commercial Rates 2025).
