Vital criteria for shipping to the U.K. via United States Postal Service priority shipping is as follows: 

Type of box length width height volume Cost weight  weight limit (lbs)  Price Per Pound  Price per Cubic inch
Small flat rate box 11 8.5 5.5 514.5 cubic inches 38.95  20 lbs  20  1.95 U.S. Dollar  0.075
Large flat rate box 13.625 11.875 3.375 546 cubic inches 49.95 20 lbs  20  2.50  0.091
Box – generic with 20 lbs indeterminate indeterminate indeterminate indeterminate 82.50 20 lbs  65  4.13  
Box – assymtotic indeterminate indeterminate indeterminate indeterminate  $220.50  65 lbs  65  3.40  

 Priority shipping is the lowest cost service available when shipping via USPS over 4 pounds.  USPS shipping rate calculator here.

It is obvious from the table if you are shipping a formless item that is  super dense that the small flat rate box is the lowest cost way to go.  

  • An example of a formless item is abrasive powder that can be conformed to any shape box.
  • a super dense item is one that reaches the weight limit of the box before it reaches the volume limit of the box

Even if the weight limit of the flat rate box is not reached before it is full of the formless item you pay a higher rate per unit volume for the larger box.  Thus the smaller box is the best price choice.

Categories: Shipping


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