USPS Flat Rate Box Comparison
Enter your package weight and shipping zone to see which USPS flat rate option beats standard Priority Mail pricing.
Flat rate max: 70 lbs
Zone = distance from origin to destination. Find your zone →
What Is USPS Flat Rate Shipping?
USPS flat rate is a Priority Mail service where the price depends only on which box or envelope you use - not on the weight (up to 70 lbs) or how far the package travels within the US. USPS provides the packaging for free, and you pay one fixed rate at the Post Office or online.
When Does Flat Rate Make Sense?
Flat rate shipping is usually the better choice when you are shipping heavier items to distant zones. The math favors flat rate when the standard Priority Mail rate for your weight and zone exceeds the flat rate price. For lightweight packages going to nearby zones, standard Priority Mail is often cheaper.
Tips for Choosing the Right Box
- Start with the smallest flat rate box that fits your item - lower price with the same coverage
- Envelopes are the cheapest option and work well for documents, clothing, and small items
- The Medium Flat Rate Box is the most popular choice for general merchandise
- Use the Large Flat Rate Box when shipping dense, heavy items to Zones 5 through 8
- Express Flat Rate Envelope is the premium option - use only when overnight delivery is required
- Order free flat rate supplies at usps.com or pick them up at any Post Office
Frequently Asked Questions
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