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.