Flat Rate vs Custom Box Shipping Comparator
Determine whether to use free USPS Flat Rate boxes (Small, Medium, Large) or your own custom box with USPS Ground Advantage or Cubic pricing for dense heavy items.
Logistics Specifications
Carrier grade math📦 Accurate client-side logistics calculation formatted for international shipping manifests.
How to Use This Tool in 3 Easy Steps
Enter Custom Box Dimensions & Weight
Input your package length, width, height, and weight.
Select Destination Zone
Choose shipping zone (Zone 1 to Zone 8).
Get Cheapest Carrier Method
See whether Flat Rate or Cubic/Ground is cheaper for this specific shipment.
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Zero data collection
Instant Speed
<5ms client execution
Mobile Ready
Native app feel
100% Free
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Frequently Asked Questions (FAQ)
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