USPS Flat Rate Boxes: Save on Flat Rate Shipping

USPS-Flat-Rate-Boxes

Using USPS Flat Rate Boxes can be a useful and cost-effective option for any small business. When you are shipping many items on a regular basis, you are going to want to find the best USPS shipping option to keep costs down and minimize the amount of time spent on organizing and shipping customer purchases. 

With USPS Flat Rate shipping, you will always know what your shipping costs are ahead of time. And the actual price of the shipment itself won’t change regardless of the weight of your package or where it’s going. As long as the item being sent fits in the size of the box that you choose and doesn’t weigh more than 70 lbs, it is good to go.

Not having to weigh each package before it is sent by USPS makes shipping a lot more convenient as well –  along with having guaranteed delivery in 1-3 business days which will make your customers very happy and keep them coming back.

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On this page

  1. How does USPS Flat Rate Shipping work?
  2. USPS Flat Rate Boxes Prices and Sizes
  3. What is included with USPS Flat Rate Shipping?
  4. USPS Flat Rate International shipping
  5. Other useful information about USPS Flat Rate Boxes

How does USPS Flat Rate Shipping work?

First, you need to pick the size of the box that you will need for the items you will be sending. USPS offers small, medium, and large boxes to choose from and the cost of the box is included in the cost of the shipping. 


USPS Priority Mail® Flat Rate Envelopes

USPS Priority Mail® Flat Rate Envelopes are a popular shipping option for sending documents, small items, and other materials. Flat Rate Envelop sizes: 

  • Priority Mail Flat Rate Envelope: 12 ½” (L) x 9 ½” (W)
  • Priority Mail Flat Rate Legal Envelope: 15” (L) x 9 ½” (W)
  • Priority Mail Flat Rate Padded Envelope 9 ½” (L) x 12 ½” (W)

USPS Priority Mail® Flat Rate Envelopes

The envelopes are made of durable material and are designed to protect the contents during shipping. When using Priority Mail® Flat Rate Envelopes, the sender does not need to weigh the package or calculate postage, as the flat rate applies regardless of weight. The envelopes can be used for domestic and international shipping, and they come with USPS tracking and insurance up to $50.

The key feature of USPS Priority Mail® Flat Rate Envelopes is that they have a flat rate, regardless of the weight or destination of the package. This makes it a cost-effective option for shipping items that are heavy or need to be delivered quickly. Priority Mail® Flat Rate Envelopes can be purchased at any USPS Post Office, online, or by phone.


USPS Priority Mail® Flat Rate Small Box

USPS Priority Mail Flat Rate Small Box is an ideal option for customers who want to send small, dense items domestically or internationally. The dimensions for USPS Flat Rate Small Box size is: 8 11/16″ x 5 7/16″ x 1 3/4″


USPS Priority Mail® Flat Rate Small Box

It is designed to fit smaller items such as jewelry, electronics, and other small products. The Flat Rate Small Box comes with a predetermined shipping cost, which is based on the weight and distance the package needs to travel, rather than the size or shape of the box.

The main benefit of using Priority Mail Flat Rate Small Box is that the shipping cost is fixed, regardless of the destination address within the United States or its territories. This can be particularly advantageous for those shipping heavier items, as the cost remains the same, even if the weight of the package exceeds the normal shipping limit for standard USPS services.

USPS provides free shipping boxes for the Priority Mail Flat Rate Small Box and the postage can be paid online or at a local USPS Post Office. Delivery time for this shipping option is typically 1-3 business days within the United States.


USPS Priority Mail® Flat Rate Medium Box

The USPS Priority Mail® Flat Rate Medium Box is a type of shipping box provided by the United States Postal Service (USPS) for Priority Mail® shipments. The USPS Flat Rate Medium Box sizes:

USPS Flat Rate Medium Box-1 Specs (top-loading):

  • Outside: 11 1/4″ x 8 3/4″ x 6″
  • Inside: 11″ x 8 1/2″ x 5 1/2″

USPS Flat Rate Medium Box-2 Specs (side-loading):

  • Outside: 14″ x 12″ x 3 1/2″
  • Inside: 13 5/8″ x 11 7/8″ x 3 3/8″

The boxes can be used to ship items that weigh up to 70 pounds.


USPS Priority Mail® Flat Rate Medium Box

One of the main advantages of using a Priority Mail® Flat Rate Medium Box is that regardless of the weight of the contents or the distance being shipped, the cost for shipping is a flat rate. This can be a cost-effective option for shipping heavier items, especially over longer distances.

The USPS provides free Priority Mail® Flat Rate Medium Boxes that can be ordered online or picked up at local post offices. The boxes are made from durable corrugated cardboard and have a pre-printed design with “Priority Mail” branding. The boxes also have self-adhesive strips for sealing and do not require any additional packaging materials.

Priority Mail® shipments using the Flat Rate Medium Box generally have a delivery time of 1-3 business days within the contiguous United States, and USPS tracking is provided.


USPS Priority Mail Flat Rate Large Box

USPS Priority Mail Flat Rate Large Box is one of the various Flat Rate options available, which means that regardless of the weight and distance of the package, the shipping cost will remain the same. It can be a convenient and cost-effective option for shipping large, and heavy items.

The Large Box option is ideal for shipping large, heavy items that can fit inside the dimensions of the box. The USPS Flat Rate Large Box Size measures 12-1/4″ x 12-1/4″ x 8″. The maximum weight limit for this box is 70 pounds. The delivery time for USPS Priority Mail Flat Rate Large Box is typically 1-3 business days, depending on the destination.


USPS Priority Mail Flat Rate Large Box

When you use the Large Box option, you will pay a flat rate for shipping, which includes USPS tracking and insurance up to $100. You can purchase additional insurance for an extra fee if you need to insure the package for a higher value.


USPS Flat Rate Boxes Prices and Sizes


USPS Flat Rate Boxes
USPS Flat Rate Box Sizes
Commercial Base Price
Post Office & Online Price
USPS Flat Rate Envelope
12 1/2” x 9 1/2”
$7.40
$7.95
USPS Small Flat Rate Envelope
10″ x 6″
$7.40
$7.95
USPS Padded Flat Rate Envelope
12 1/2” x 9 1/2”
$8.00
$8.55
USPS Legal Flat Rate Envelope
15″ x 9 1/2″
$7.70
$8.25
USPS Small Flat Rate Box
8 11/16″ x 5 7/16″ x 1 3/4″
$7.90
$8.45
USPS Flat Rate Medium Box 1 (top loading)
11 1/4″ x 8 3/4″ x 6″
$13.75
$15.50
USPS Flat Rate Medium Box 2 (side loading)
14″ x 12″ x 3 1/2″
$13.75
$15.50
USPS Large Flat Rate Box
12 1/4″ x 12 1/4″ x 6″
$19.30
$21.90
USPS APO/FPO/DPO Flat Rate Box
12 1/4″ x 12 1/4″ x 6″
$17.80
$20.40
USPS Large Flat Rate Board Game Box
24 1/16″ x 11 7/8″ x 3 1/8″
$19.30
$21.90

A perk of using the same-sized boxes consistently is that you can offer your customers the option at checkout to add more to their order for the same shipping costs – if they still have room in the box!

Once you choose and purchase the right size of box for sending your product you are ready to go. There is no need to have the package weighed since the price stays the same. You just need to ensure that the weight does not exceed 70 lbs. Shipping labels can be printed right at your home or office and you just need to drop off your packages at any USPS store or take advantage of the Free Package Pickup service right from your home or office. It’s as easy as that.


What is included with USPS Flat Rate Shipping?

Along with the packaging, there are other features that will be included with the USPS Flat Rate Box. There is no need to purchase shipping insurance since every Flat Rate package is automatically insured for up to $50 – which will cover any lost or damaged items sent. Another convenience that is included is real-time tracking so that both you and the recipient are able to keep track of the package right up until its delivery.

Customers won’t be required to seek out the USPS website to find out where their recent purchase is and when it will arrive. They can revisit your website, click a link in your email, or even receive text alerts to see how their package is doing. You can integrate USPS’ APIs into your website with PluginHive to quickly benefit from the advantages that using USPS services directly from your Shopify, WooCommerce, or another eCommerce platform provides.


USPS Flat Rate International shipping

Shipping parcels at a flat rate is an easy and cost-effective method of shipping internationally. With USPS Priority Mail International, shipments to over 180 countries are guaranteed to arrive within 6-10 business days. These countries include close neighbors Canada and Mexico, and as far as Australia. 

According to the USPS website, you can either ship “using free Flat Rate Boxes and Envelopes (envelopes and small boxes up to 4 lbs, medium and large boxes up to 20 lbs), or ship by weight for packages up to 70 lbs.” You can choose whichever option is best and least costly for your eCommerce business. All customs documents and information is taken care of automatically through the USPS app, your website, or the method you choose for generating the label for your flat rate box. 

  • USPS offers insurance for flat-rate boxes up to $200 for merchandise and products. 
  • Packages may qualify for free Package Pickup from either your office or business.
  • Tracking is also included in all international flat-rate packages. Your customers can know exactly where their parcels are at all times right from your website. 

Offering USPS flat rate boxes also allow your international customer to purchase more products without having to pay extra shipping. If there’s an option at the checkout that tells customers (this can be done via PluginHive) that they still have room within their box for the same shipping price, they may be likely to add more to their cart. 


Other useful information about USPS Flat Rate Boxes

Flat Rate Shipping Boxes are sent using USPS’s Priority Mail service which means that your package will reach its destination in 1-3 business days which is great for keeping your customers happy. Any packages that are over the maximum weight limit of 70 pounds or do not fit within those boxes provided by USPS will need to be shipped separately using traditional methods of shipping.

If you have a Commercial business account with USPS, you will receive discounted rates and services that make any of the USPS shipping rates or options easy to use. 


PluginHive allows eCommerce store owners to completely streamline their USPS shipping process right from cart to doorstep through real-time shipping prices, tracking options, automation of shipping labels and more. Learn more about automating USPS shipping into your Shopify, WooCommerce, or another eCommerce platform by reaching out to our customer support team.