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USPS® Priority Mail Large Flat Rate Box Shipping Without Guesswork
The USPS Priority Mail Large Flat Rate Box gives you predictable Priority Mail speed with one simple rate for the box, even when your order gets heavy. With ShipStation, you can compare USPS rates against other carriers, and print labels faster from one dashboard.
Connected to the platforms that power your business
Predictable shipping, faster days in the warehouse
When you want cost control and quick delivery, ShipStation helps you choose the right Flat Rate option, automate decisions, and reduce clicks across your workflow while keeping buyers updated with branded tracking.
Know the rate before you tape the box
When you choose the Large Flat Rate Box, ShipStation shows the rate inside your workflow. Plan margin and shipping charges with confidence. You can also compare costs against other carriers in real time.
Move from paid order to printed label, fast
Avoid retyping addresses or switching between tabs. ShipStation pulls orders from your stores and marketplaces, then lets you create labels one at a time or in batches. Use automation and presets to create up to 15x more labels per hour. Reduce manual steps. Minimize errors—so your team can ship quickly even during high-volume periods.
Keep your brand in the box experience
The label is only part of the moment. With branded tracking pages and notifications, your customer sees your logo and tone, not a generic carrier page. Add returns workflows so customers can self-serve and you spend less time on “Where’s my order?” emails.
USPS Priority Mail Large Flat Rate Box results — one price, zero surprises
We’ve helped 130,000+ businesses automate labels and compare shipping costs using the USPS Priority Mail Large Flat Rate Box. Let us help you decide when flat rate is the right call, too.
4.9 rating 67 reviews
4.6 rating 897 reviews
4.3 rating 531 reviews
Get Flat Rate right with USPS tools that scale
From setup to label creation, ShipStation makes it easy to choose the right Flat Rate option, automate decisions, and batch print labels. Compare rates across carriers like UPS®, FedEx®, and DHL Express® to ensure every shipment uses the best option.
What is the USPS Priority Mail Large Flat Rate Box
It’s USPS packaging that ships for a set Flat Rate when you use Priority Mail. The main win is predictability: price is based on the box, not distance, making it a strong choice for dense or heavy orders.
Configure Label
USPS from ShipStation · 02494 → 78701
Service
USPS Priority Mail
Package
Large Flat Rate Box
Large Flat Rate Box
USPS Priority Mail · Flat Rate
$28.06
One price, based on the box, not the distance
Zone 1 · Boston, MA
$28.06
Zone 5 · Austin, TX
$28.06
Zone 8 · Seattle, WA
$28.06
Priority Mail Large Flat Rate Box dimensions
USPS offers more than one Large Flat Rate Box style, and the exact priority mail large flat rate box dimensions are printed on the box you’re holding. Measure your packed box and match it to the correct package type in ShipStation so your label and acceptance scan go smoothly.
USPS Large Flat Rate Box shipping cost
Flat Rate is about simple math. Cost is set by the Flat Rate product, so you can forecast spend without guessing zones. In ShipStation, the rate shows while you rate shop, helping you compare services and review cost and pricing across orders.
Rates
Canada Post · 4 services
M5V 2T6 → V6B 1A11 kg25 × 20 × 10 cm
Canada Post Regular Parcel™
6 Days
$5.13
Canada Post Expedited Parcel™
4 Days
$8.27
Canada Post Xpresspost™
2 Days
$14.46
Canada Post Priority™
1 Day
$62.51
View By: All Rates
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Weight limits for Priority Mail Large Flat Rate Box
USPS allows heavy packages in Flat Rate packaging, up to the Priority Mail limit of 70 lbs. That makes the Large Flat Rate Box popular for compact, weighty items. In ShipStation, you can use the weight limit for large flat rate box shipments as a rule trigger to automatically assign Flat Rate packaging and reduce manual decisions.
Awaiting Shipment
Order #
Recipient
Carrier
SH-59744
Sofia Vasquez
Canada Post
AZ-44198
Edith Wong
UPS
EB-A8210
Antonio Ellis
GlobalPost
SH-59743
Cecilia Edwards
UPS
SH-59742
Tara Simon
Canada Post
EB-A8209
Rushina Singh
UPS
SH-59741
Ming Zhao
UPS
AZ-44197
Zara Wells
GlobalPost
AZ-44196
Priya Rivas
Canada Post
Automation Rules
Rule Name
Last Modified
Active
Actions
Set Package Dimensions for 2 Items
10/15/2024
Tag for Orders Over 2.0 kg
10/15/2024
Set Carrier to Canada Post
10/15/2024
Insure Package
09/29/2024
Set International Orders to GlobalPost
09/05/2024
Default Confirmation
08/26/2024
Create Rule
When to use a large flat rate box for shipping
Use it when weight climbs and you want steady pricing and fast delivery. It’s often a good fit for items like:
- Small hardware, tools, and auto parts that are dense
- Bundled apparel, books, or boxed sets that pack tight
If your item is big but light, you may save more with other packaging and services.
Print Priority Mail Flat Rate Labels with ShipStation
Ready to ship? Connect your stores through integrations, pull orders into one grid, then print single labels or run batch label printing for the day’s shipments. Add automation rules based on weight, SKU, tag, or destination—so every order gets the right service automatically.
Awaiting Shipment
672
Amazon
81
BigCommerce
28
eBay
79
Shopify
63
FAQs about USPS Priority Mail Large Flat Rate Box shipping
What's the weight limit for large flat rate box shipments?
The Large Flat Rate Box supports heavy shipments up to the USPS Priority Mail Flat Rate limit of 70 lbs. Confirm your packed weight, tape seams well, and avoid bulging. If it won’t close normally, pick a different box.
Can I use a Large Flat Rate Box with USPS services other than Priority Mail?
No. They are only an option when you select USPS Priority Mail in ShipStation. If you choose another service, the Flat Rate option won’t apply.
Do I need to enter dimensions for a Flat Rate box?
Flat Rate pricing is tied to the package type, but shipment data still matters. Be sure to enter accurate details when you ship. Clean inputs help prevent adjustments and keep rate comparisons reliable.
How do I compare Priority Mail Flat Rate shipping costs to other carriers?
In ShipStation, you can rate shop in the same screen where you create labels. Compare Flat Rate against services from USPS, UPS, FedEx, and DHL Express without leaving your workflow.
What are the best products to ship in flat rate boxes?
Dense items that pack tight tend to win. Think parts, kits, and bundles that would be pricey by distance-based rates. For light items, other services may be more cost-effective.
How does ShipStation help with returns after I ship Flat Rate orders?
Use branded tracking and a returns portal to reduce support load. Your customer can start a return, follow updates, and stay inside your brand. Your team gets cleaner workflows and fewer manual emails.