Standard USPS Priority Mail rates are calculated by our online store.  Standard mail rates are based on maximum box size of 12"X12"X12".  Most orders will be able to mail out in boxes up to this size.  Due to new strict mailing guidelines, larger orders that ship out in boxes bigger than 12"X12"X12", will be subject to additional postage.  An email invoice notification for additional postage will be sent to you before your order is shipped.  Mahalo for your understanding.