Flat Rate Shipping
What flat rate shipping is, when to use it, and how it compares to weight-based pricing.
What Is Flat Rate Shipping?
With flat rate shipping, the price is predetermined based on the box size you choose, not the weight of your package or how far it's traveling. USPS offers small, medium, and large flat rate boxes as well as flat rate envelopes, each at a specific price point. This makes flat rate ideal for heavy items shipping long distances, since a 50 lb item costs the same as a 5 lb item in the same box. However, flat rate is not always the cheapest option -- for lightweight packages or short-distance shipments, weight-based pricing or cubic pricing often costs less. FedEx and UPS also offer flat rate-style services like FedEx One Rate.
Example
A USPS Medium Flat Rate Box costs around $16.10 (commercial price) regardless of weight up to 70 lbs. If you're shipping a 20 lb item from New York to California, flat rate could save you $15+ compared to weight-based pricing. But if that same box only weighs 2 lbs, you'd overpay significantly.
Why It Matters
How Each Carrier Handles Flat Rate Shipping
USPS
USPS offers Priority Mail Flat Rate in several sizes: Envelope ($8.40 commercial), Small Box ($9.45), Medium Box ($16.10), and Large Box ($21.60). All include tracking and $100 insurance. Free boxes are available at post offices or usps.com.
FedEx
FedEx offers FedEx One Rate, a flat rate pricing option for FedEx Express services. Pricing varies by package type and speed (overnight, 2-day, etc.) but is fixed regardless of weight up to 50 lbs. Boxes must be purchased or provided by the shipper.
UPS
UPS offers UPS Simple Rate, a flat rate option for packages within certain size categories. Pricing is based on box size and delivery speed. Available for UPS Ground, 3 Day Select, 2nd Day Air, and Next Day Air.
Tips
Related Terms
Cubic Pricing • Zone-Based Pricing • Ground Advantage
Frequently Asked Questions
No. Flat rate is most cost-effective for heavy packages shipping long distances. For lightweight items or short-distance shipments, weight-based pricing through Ground Advantage or cubic pricing is usually cheaper.
USPS provides Flat Rate boxes and envelopes for free. You can order them online at usps.com/store, pick them up at any post office, or request free delivery to your address. You must use the official USPS Flat Rate boxes to get flat rate pricing.
USPS Flat Rate boxes have a 70 lb weight limit. FedEx One Rate has a 50 lb limit. As long as your item fits in the box and doesn't exceed the weight limit, the price stays the same.
No, for USPS Priority Mail Flat Rate you must use the official USPS-branded Flat Rate boxes or envelopes. You cannot use your own packaging and receive flat rate pricing. However, FedEx One Rate and UPS Simple Rate allow the use of your own packaging within size limits.
Start Shipping Smarter
I'd Ship That automatically handles flat rate shipping calculations so you always get the best rate.
Start Shipping Free