Shipping Discount - Shows for some package sizes, not others.

[mrs_b*s_collectibles_and_more]

I've been doing some listing this week while I have some time and am confused by the shipping discount. If I mark the package size 12 x 12 x 12, it shows the discount. If I change the package size to, say, 12 x 10 x 8 the discount disappears. Weight and shipping method not changing, just the size of the package. Some of my smaller items don't need a 12 x 12 x 12 box. Am I missing something in the 'rules'. 

Thanks in advance. 

[rfmtm]

All carriers now base rates on Dimensional Weight as well as Actual Weight.  You are charged for whatever is higher.

[richard1rst]

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@rfmtm wrote:

All carriers now base rates on Dimensional Weight as well as Actual Weight.  You are charged for whatever is higher.

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NOPE

Cubic pricing is also based on dimensional size and the actual weight is irrelevant. Frequently, almost always, cubic dimensional package are CHEAPER than the same weight in a "regular" sized box.

[mrs_b*s_collectibles_and_more]

So, If I listed a 2 pound item with a 12 x 12 x 12 box, and then use a 8 x 6 x 6 box to ship, I'll be charged more? That doesn't make sense. 

[richard1rst]

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@mrs_b*s_collectibles_and_more wrote:

So, If I listed a 2 pound item with a 12 x 12 x 12 box, and then use a 8 x 6 x 6 box to ship, I'll be charged more? That doesn't make sense. 

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@mrs_b*s_collectibles_and_more 

You misunderstand. NO you will be charged LESS.

My comment was a refutation of the post by rfmtm which said (in reference to dimensional sizes) "you will be charged whichever is higher". And in fact you will not. The point being that (as in the case you cited) dimensional sizes sometimes can be LOWER than weight based shipments.

And here is an interesting wrinkle. As the weight of the 8x6x6 goes UP the shipping price remains the SAME.

[rfmtm]

Yes, sorry I was posting from a boiler plate before cubic was generally available.  So thanks for the clarification.

[mrs_b*s_collectibles_and_more]

Thank you for the clarification. It's just weird that it doesn't show me a discount when creating listing unless I put in the larger dimensions. 

[rfmtm]

The cubic discount is limited to a max of .5 cubic foot (or 20 pounds or 18" long).  The 12x12x12 is 1 cu ft, while the 8x6x6 is only .288 cu ft.

Cubic Rate is calculated as follows:
Cubic Box OD = L" x W" x H" / 1728 Round Down all dimensions to lowest quarter inch before calculation, then Round Up the result to the next .1 cubic foot.
Cubic Max OD = 0.500cu ft
Cubic Max Weight = 20#
Cubic Max Length = 18"L

[deserdog]

Ground Advantage also has cubic rutes, up to 1 cubic foot