Do the dimensions of a box, greatly determine the cost of shipping. Or do all factors play a role in shipping costs?

With UPS , USPS AND FEDEX . Does weight , dimensions , and distance , also quantity of boxes, all play a factor in determining how much it will cost to ship a box or several boxes? A representative told me that I can save money by taking the items which I'm shipping out of the larger size boxes and placing... show more With UPS , USPS AND FEDEX . Does weight , dimensions , and distance , also quantity of boxes, all play a factor in determining how much it will cost to ship a box or several boxes?

A representative told me that I can save money by taking the items which I'm shipping out of the larger size boxes and placing them into smaller size boxes is this true?
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