Per Box and Box Size Charges
Bigger is not necessarily better.
Many shippers erroneously think that it will cost them less to ship one large box rather than several smaller or medium sized ones.
The most general rule is to not use any boxes smaller than 12 x 12 x 12 and to not fill a box with more than 70 lbs. Used boxes are fine and used, commercial boxes are usually stronger and better than typical moving and storage boxes which are only single walled cardboard.
UPS and FedEx Ground parcel services charge an additional per box fee of a couple dollars. But if you go over 70 lbs in a single box, they will charge an OVER-WEIGHT FEE of $8.00 USD for each box over 70 lbs. Also, they will charge an OVERSIZE fee starting at $50.00 USD for boxes that are more than 130 inches in circumference at the thickest measurement and will refuse boxes of more than 165 inches in circumference.
For shipping multiple boxes by freight, within the US and internationally, you are not billed per box. You are billed by total weight and dimensional factors. Our recommendation for the shipping of books and clothing is to use boxes no smaller than 12 x 12 x 12 inches and no larger than 24 x 24 x 24. Sizes in between these two extremes are generally sturdy enough to ship a combination of items. If you try and fill a 24 x 24 x 24 inch box of books, it is going to weight more than 100 lbs and you are not going to be able to lift it. Also, if you have boxes that are heavier than 70 lbs, lift gate equipment may be required for pickup and that can add $30.00 to $100.00 to the total costs.
"My box is too large. I have empty space." Cut at the corners where the walls meet. Score the outside of the box between the cuts and then fold over across the top making the cut line the new top edge. Here is a video. This will save you space, money and better protect the contents.