Flat Rate Shipping Boxes – Pricing and Other Aspects to Consider

One of the common worries that arise among eCommerce vendors is about choosing a standard shipping service. Regardless of what you choose, the shipping options must be fast and economical and should be designed to enhance customer expectations. The greatest challenge that arises in managing eCommerce is striking a perfect balance between shipping speed and cost-saving efforts. It is said that almost 28% of the shoppers are abandoning the cart because of unexpected shipping costs.

What is Flat Rate Shipping?

Flat rate shipping is when a uniform or a single rate is charged for shipping a package, regardless of its weight or size as long as the package weighs less than 70 lbs. Hence compared to other shipping options, flat rate, as the name says, charges only a flat rate depending upon the package size. The best part of using flat rate shipping is that the eCommerce vendors can send orders of any weight and pay the uniform charge applied for the flat rate option provided the package is of the same size.

How Does Flat Rate Work?

The size, weight, and dimension of the package do not affect flat rate shipping. What does play a vital role is the size of the boxes used in shipping. Here are steps to follow, when you are using the flat-rate option for shipping.

  • Get flat rate shipping boxes from a shipping courier
    It is always ideal to make use of the shipping boxes provided by the courier itself to ensure that you fit into the criteria of flat-rate shipping. All you need to do is just pack the items and then ship them. You can choose from a variety of boxes of sizes – small, medium, and large boxes. Large boxes will cost you a little more than the smaller and the medium ones. In any case, the maximum weight should not cross 70 lbs.
  • Pack the items and address the box
    The next thing you need to do is to pack the item in the box you purchased and then secure them following the packaging guidelines and then label them. Remember to address the package correctly following the addressing formats.
  • Send your package
    Choose the shipping carrier using which you want to send the package and then ship it. You can either drop the package at the nearest drop-off center or even opt for a pickup.

Things to Consider before using flat rate

Even though flat rate shipping is considered the most economical choice, there are many things you need to keep in mind while preparing your shipments.

Size of the Box: Flat rate shipping mostly applies to certain boxes and packaging, which are to be purchased from the shipping provider itself. 

Weight: The weight of the shipment is not a matter unless the weight of the shipment is under the provided weight limit.

Packaging: You need to ensure the package is correctly sized to qualify for flat-rate shipping. 

Items to Ship: As long as the items are not listed as prohibited items you can ship anything that can fit into the boxes accurately.

Flat Rate Shipping Options & Costs

If you see, most popular shipping options do provide options to ship at a flat rate. So here we are taking a look at the various flat rate options and costs associated with it.

FedEx Flat Rate Shipping

Image of a FedEx Medium Box || flat rate shipping boxes

FedEx Flat rate shipping option, or the FedEx One rate, is the flat rate shipping option provided by FedEx. The cost is completely determined by the distance the package travels and the package’s size. The price depends on the FedEx box or packages you sent the items in. Hence, the bigger the box, the higher the cost will be. Here is a brief list of prices:

FedEx 3rd Day 2nd Day Overnight
Envelope $8.50 $18.90 $26.15
Small Box $9.50 $20.95 $34.60
Medium Box $12.35 $22.15 $38.90
Large Box $19.05 $24.00 $45.25
Extra Large Box $30.85 $34.00 $51.35


Here are the features of FedEx One Rate:

  • It is indeed cost-saving because it’s free when using FedEx Express shipping.
  • You don’t have to spend time weighing the packages as long as the package weight falls within 50 lbs and the envelope under 10 lbs.
  • No surprise costs as the costs are predetermined for flat-rate shipping.
  • There are 12 flat rate boxes options available.
  • Delivery happens within 1,2 or 3 days.
  • Easy to schedule pickups or drop off at a nearby location.
  • You get a money-back guarantee with the FedEx Moneyback Guarantee.

USPS Priority Flat Rate

USPS is a popular flat rate shipping option whenever you consider flat rate shipping. The maximum size allowed is 70 lbs. USPS offers a wide range of flat rate boxes for shipping. The pricing is completely dependent on the size of the shipment.

USPS Priority Overnight
Envelope $7.75 $26.35
Padded envelope $8.40 $26.95
Small box $8.30 N/A
Medium box $15.05 N/A
APO/FPO Large Box $19.60 N/A
Large Box $21.10 N/A



  • Offers delivery within 1-3 Business Days
  • Free Package Pickup service is available at your home or office as per the schedule.
  • Includes USPS Tracking and up to $50 of insurance with most shipments. (restrictions apply).
  • There are no fuel surcharges, especially for resident or rural delivery, or for Saturday delivery.
  • Flat Rate, regional, and prepaid pricing (retail only) are available for all shipping.
  • Prepaid Forever Priority Mail Flat Rate: Except for Priority Mail Flat Rate packaging, Priority Mail prices are mostly based on weight and shipping zone. With Prepaid Forever Priority Mail Flat Rate, you get the same Flat Rate pricing with the added convenience of Forever postage.
  • The minimum weight required is 70 lbs with a maximum combined length and girth should be 108 inches.

Read more about USPS Flat Rate options.

UPS Simple Rate

Unlike the other shipping options, UPS allows eCommerce vendors to use their own boxes or envelopes for shipping. However, the package shouldn’t exceed 50 lbs, and the size should be an equivalent of 12x12x12 cubic inches. The prices do not change regardless of the shipping destination. The cost is completely on the size of the package and the shipping service chosen.

UPS Ground 3-Day 2nd Day
Xtra Small $8.25 $13.75 $16.75
Small Box $10.75 $16.50 $19.95
Medium Box $13.00 $23.50 $25.50
Large Box $17.50 $31.50 $45.50
Extra Large Box $21.75 $40.00 $59


  • Maximum volume up to 1,728 cubic inches.
  • The shipping options UPS Ground, 3 Day Select, 2nd Day Air, and Next Day Air Saver can be used for delivery speed.
  • You get to use 5 flat rate shipping options with countless packaging possibilities.
  • You can also use your customized packing.

So overall, here is a brief comparison of the three popular flat rate shipping options.

Features UPS FedEx USPS
Customer Packaging Available Use only FedEx flat rate boxes. Use only USPS flat rate boxes.
Maximum Volume Up to 1,728 in3 Up to 1,452 in3 Up to 900 in3
Shipping Speeds UPS Ground, 3 Day Select, 2nd Day Air, and Next Day Air Saver  Express Services only (no Ground) Priority Mail, 1-3 business days
Declared Value $100 $100 $50
Shipping Rates National Flat Rate 3 Zones, National Flat Rate

How Long Does Flat Rate Shipping Take?

The time taken for delivery completely depends on the service you choose. For example, FedEx One Rate shipping is available for FedEx Express saver, second-day delivery as well as overnight delivery. And when you are shipping with USPS, most of the shipments take around 1-3 business days to deliver the package. On the other hand, the UPS flat-rate option, UPS Simple Rate can be used with UPS Ground, 2nd-day air, and 3-day select shipping services.

Cost to Ship Flat Rate Boxes

As mentioned earlier, the cost to ship flat rate boxes is based on the package’s size and distance for the corresponding flat rate option chosen like FedEx one rate. Shipping carriers provide small, medium, and large flat rate shipping boxes with varying prices. For example, FedEx’s small envelope approximately costs around $8.50 while the large box costs you around $34.90. UPS offers five different sizing options and charges $8.25 for the small package and $21.75 for a large package. The USPS flat rate shipping option costs almost $7.15 for a small package and $8.30 for a large package.

Flat Rate Shipping and International Shipping Rates

Flat rate options can come in handy when you are shipping internationally, but the shipping rates vary with the shipping zones. Some shipping options have fixed shipping rates within the contiguous United States and higher rates for Hawaii and Alaska. Most of the time, the cost of flat rate shipping depends on the package size chosen.

Benefits/Drawbacks of Flat Rate Shipping

Some benefits for eCommerce merchants include:

  • You can send packages up to 70lbs without worrying about the shipping cost.
  • Provide automatic shipping insurance.
  • Drop off at any store location or post boxes.
  • Shipping services offer prompt tracking services.

Drawbacks include:

  • eCommerce businesses lose branding opportunities for using the shipping companies’ box.
  • Likely to be expensive for lightweight packages
  • Will be costly to ship domestic orders.

How to integrate flat rate shipping boxes into your WooCommerce store?

Let’s consider USPS flat rate options, which are most commonly in use by most of the eCommerce store owners. To integrate the USPS flat rate options onto your WooCommerce store, you can simply use the following plugins:

Once you install these plugins in your store, you can make use of the USPS shipping services. Moreover, you get the various flat rate options provided by USPS here.

flat rate shipping boxes

As you can see, you get the above-shown flat rate shipping options on your store, which you can use while shipping. Here are the rates for using USPS flat rate shipping currently.

Packaging Dimensions Maximum Weight (Domestic) Cost (Domestic, Retail Price) Maximum Weight (International) Cost (International, Retail Price)
Flat Rate Envelope 12 1/2″ x 9 1/2″ 70 lbs $7.75 4 lbs $26.90
Small Flat Rate Envelope 10″ x 6″ 70 lbs $8.05 4 lbs $26.90
Padded Flat Rate Envelope 12 1/2″ x 9 1/2″ 70 lbs $8.40 4 lbs $26.90
Small Flat Rate Box 8 11/16″ x 5 7/16″ x 1 3/4″ 70 lbs $8.30 4 lbs $26.85
Medium Flat Rate Box – 1 (Top-Loading) 11 1/4″ x 8 3/4″ x 6″ 70 lbs $15.05 20 lbs $51.50
Medium Flat Rate Box – 2 (Side-Loading) 14″ x 12″ x 3 1/4″ 70 lbs $15.05 20 lbs $51.50
Large Flat Rate Box 12 1/4″ x 12 1/4″ x 6″ 70 lbs $21.10 20 lbs $67.05


Is flat rate shipping ideal for your business?

Choosing flat rate shipping completely depends on what you want to ship and where you want to ship to. While flat rate shipping is considered a good option, there might be certain instances, where flat-rate options may not be apt for shipping. It is always good to consider various factors before you choose a flat rate for your shipping.

Further Reading:

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