Flat Rate shipping: Rates, prices and how it works.

Flat rate shipping is a way to keep shipping expenses low while adding predictability. The rate is based on the size of the package, so long as it weighs less than the carrier’s pre-set limit.

What is flat rate shipping?

It’s a service offered by the major shipping carriers. The carriers charge a single fixed rate based on the size of a box or envelope rather than its weight. The larger the flat rate box, the more it will cost to ship. As a shipping method, flat rate is preferred by many shippers for its convenience, although it may not always be the lowest-cost shipping option available. Up to a certain weight, there is valuable predictability in flat rate shipping, meaning it virtually eliminates the need to weigh packages if the contents weigh less than 70lbs for USPS or 50lbs for UPS and FedEx.

The major carriers’ flat rate options are called USPS Priority Mail® and FedEx One Rate®. All are limited to domestic shipping, although USPS priority flat rate mail offers shipping to military bases and embassies overseas.

if you want to know whether flat rate shipping is the best option for your package, multi-carrier shipping software can help you make the right decision. If flat rates are included in your negotiated UPS and/or FedEx rate card, you can simply import them into PitneyShip™ or PitneyShip™ Pro to see a comparison of the available rates and delivery dates.

USPS and FedEx require that you use their flat rate packaging. UPS is the exception to the rule: it offers shippers the option to purchase branded packaging or use their own packaging.

How does flat rate shipping work?

To take advantage of flat rate shipping costs, simply follow these three simple steps.

  • Step One: Obtain a flat rate shipping box or envelope from your shipping carrier. There is no cost for an envelope when using flat rate shipping—you’ll pay only the small flat rate cost, the envelope itself is free. There are various package types and sizes to choose from as well, and this packaging is also free. You can place an order online or pick up packaging at the local Post Office or carrier store.
  • Step Two: Place the items to be shipped in the envelope or flat rate box and affix the shipping label with the address. Because the price is determined by the size of the package, you may be able to include more items in a single flat rate shipment without increasing your shipping cost. Just be sure that all flaps on the package can be closed completely.
  • Step Three: Bring your package to the Post Office or call to arrange a free pickup for the box using USPS flat rate. If you are shipping via FedEx or UPS, you can either schedule a pickup by phone or online or you can drop the package off at a nearby carrier shipping location.

What does flat rate shipping cost?

Flat rate shipping charges vary by carrier, shipping speed and the type of flat rate packaging used. Multi-carrier shipping software can make finding the best flat rate shipping option fast and easy. You can compare rates from USPS, UPS and FedEx in just a few clicks, and identify the best combination of price and delivery date with far less time and effort. In contrast, for example, if you wanted to know the lowest cost to send a large package from New York to Seattle using flat rate shipping, you would have to go to each carrier’s website and enter all the data, including the address you are shipping from and the name and address of the intended recipient. This process is repetitive, time consuming and potentially confusing.

USPS flat rate shipping packaging

The USPS Priority Mail has the lowest flat rate shipping charges, but it offers fewer packaging options. Commercial rates are available to shippers using a postage meter or shipping software. USPS flat shipping rates include online tracking and up to $100 insurance (for most shipments) at no additional cost. Insurance may be purchased for shipments valued at more than $100.


USPS flat rate packaging options

Flat rate envelope 12-1/2” x 9-1/2”
Small flat rate box 8 5/8″ x 5 3/8″ x 1 5/8″ (inside)
Medium flat rate box:  
Top loading 11″ x 8 1/2″ x 5 1/2″ (inside)
Side loading 13 5/8″ x 11 7/8″ x 3 3/8″ (inside)
Large flat rate box 12″ x 12″ x 5 1/2″ (inside)
Large flat rate board game box 23 11/16″ x 11 3/4″ x 3″ (inside)
APO FPO DPO flat rate box 12″ x 12″ x 5 1/2″ (inside)

UPS flat rate shipping packaging

UPS Simple Rate has the greatest variety of flat rate box sizes and the highest maximum package volume at 1,728 cubic inches, but it does not offer small flat rate cost options like envelopes, tubes or packs. Its flat shipping rates are generally higher than USPS and lower than FedEx.

UPS flat rate packaging options

Extra small flat rate box 4” x 4” x 4” 6” x 4” x 4” 8” x 6” x 2”
Small flat rate box 6 “ x 6 “ x 6 “ 8 “ x 6 “ x 5 “ 12 “ x 9 “ x 2 “
Medium flat rate box 8 “ x 8 “ x 8 “ 12 “ x 9 “ x 6 “ 13 “ x 11 “ x 2 “
Large flat rate box 10 “ x 10 “ x 10 “ 12 “ x 12 “ x 7 “ 15 “ x 11 “ x 6 “
Extra-large flat rate box 12 “ x 12 “ x 12 “ 16 “ x 12 “ x 9 “ 18 “ x 12 “ x 6 “

FedEx flat rate shipping packaging

FedEx One Rate® provides the most packaging options for flat rate shipping. It is the only carrier that offers flat rate packs and tubes. While FedEx flat rate shipping prices tend to be the highest of the three major carriers, its Pak option is quite versatile and competitively priced.

FedEx flat rate packaging options

Envelope 9-1/2" x 12-1/2" 9-1/2" x 15-1/2"
Pak 10-1/4" x 12-3/4" 12" x 15-1/2"
Small box 10-7/8" x 1-1/2" x 12-3/8" 8-3/4" x 2-5/8" x 11-1/4"
Medium box 11-1/2" x 2-3/8" x 13-1/4 8-3/4" x 4-3/8" x 11-1/4"
Large box 12-3/8" x 3" x 17-1/2" 8-3/4" x 7-3/4" x 11-1/4"
Extra-large box 11-7/8" x 10-3/4" x 11" 15-3/4" x 14-1/8" x 6"
Tube 6" x 6" x 38"  

* As of September 2022

How long does flat rate shipping take?

The best answer to the question “how long does flat rate shipping take” is “it depends.” Flat rate parcels shipped domestically via USPS Priority Mail® will arrive within one to three business days. For an even faster flat rate shipping time, Priority Mail® Express guarantees delivery of flat rate envelopes in one to two days at a higher cost.

UPS Simple Rate offers a choice of four different flat rate shipping speeds: delivery within five days, within three business days, second day and next-day delivery.

FedEx One Rate® also offers multiple flat rate shipping speeds which vary by both the delivery day and time. FedEx First Overnight, Priority Overnight and Standard Overnight all arrive the next day, by 8:30am, 10:30am and 3:00pm respectively. For two-day delivery, FedEx 2Day AM packages arrive by 10:30 am and FedEx 2Day packages by 4:30pm. The slowest and most economical option, FedEx Express Saver, delivers on the third day by 4:30pm.

Which flat rate shipping option should I choose for my business?

Choosing the best flat rate delivery service for your business can be complicated for two reasons. First, the USPS, UPS and FedEx flat rate shipping services are similar in many ways. Secondly, you need to take a variety of factors about your business into consideration.

Ask yourself: how standardized are the items that you ship? How geographically dispersed are your customers? How much are they willing to pay for shipping and how quickly do they expect to receive their purchases?

Is branded packaging an important part of the customer experience? UPS is the only carrier that offers flat rate packaging branded with your logo. In some cases, they may also give you flat rate pricing when you use your own packaging. (You can take advantage of this option if you import your negotiated UPS rates into the PitneyShip™ software.)

Price may be the biggest deciding factor. The USPS and UPS allow you to ship anywhere in the US for the same flat rate. By contrast, FedEx divides the country into multiple zones: the farther you ship, the more you pay. The cost difference can be substantial. However, if you need to guarantee delivery early in the day, then FedEx is your only option. If delivery on Sundays or holidays is required, Priority Mail may be your best choice.

It’s also important to realize that you don’t have to pick just one flat rate shipping carrier. Different products and situations may call for a different approach. For example, FedEx is the only carrier with a flat rate shipping tube that is ideal for shipping very long narrow items like golf clubs or baseball bats.

Why use flat rate shipping for your business?

Businesses that use flat rate shipping services benefit in many ways. These services can reduce shipping costs and streamline the fulfillment process. They eliminate packaging expense and simplify free shipping promotions that customers love.

Flat rate shipping costs are predictable.

Unlike standard shipping rates, flat rates remain consistent throughout the year, and there are no surcharges for fuel, peak season or residential delivery. This makes it easy to calculate flat rate shipping costs, so you can budget and ship cost-effectively.

Flat rate shipping boxes are free.

To keep package size and weight standardized, carriers supply flat rate packaging in a variety of shapes and sizes at no cost. Eliminating packaging expense can be particularly valuable to new businesses.

Flat rate shipping saves time on order fulfillment.

Because there’s no need to weigh each individual package, flat rate shipping gets your orders out the door faster and reduces labor costs. This is especially important if you are fulfilling orders in-house.

Flat rate shipping rates automatically include tracking and insurance.

USPS flat shipping rates include online tracking and up to $100 insurance (for most shipments) at no additional cost. Insurance may be purchased for shipments valued at more than $100. Both FedEx One Rate and UPS Simple rate shipping offer free tracking and cover repair or replacement of declared value up to $100 for no additional charge.

UPS and FedEx flat shipping rates include a money back guarantee.

If for some reason your flat rate package is not delivered on time, both UPS Simple Rate and FedEx One Rate will issue a refund on your shipping charges.

What are the advantages of using flat rate shipping with PitneyShip?

Once you’ve looked at your business needs and determined that flat rate shipping is right for you, Pitney Bowes is ready help you make the smart shipping decision for every package you send.

PitneyShip™, our solution for businesses that ship less than one hundred packages per month, makes it simple. You can automatically access USPS flat rate shipping options, but that’s not all. If you have flat rate shipping included in your UPS or FedEx accounts, you can also import those into the program to compare rates and select the right flat rate delivery service for each and every shipment.

If your shipping volume is higher, PitneyShip™ Pro will give you all of the above benefits plus deeply discounted UPS rates, real time data for visibility into all your shipping activity, and scalability to support multiple users across multiple locations.