Does shipping automatically change if they order two in one box?

[CK_701]

So if the customer orders a two-pack i need to use a bit larger box and the wight goes up.  IN the shipping preferences I put the size of this two-pack box... now will Shopify automatically charge the correct shipping for a two-pack?   

If not , pls tell me how to make this happen.    Been searching and searching and cant find definitive answer.  

-scott