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postcalc.usps.com]
NW Florida is zone 5 for you, so is Little Rock, AR, Tulsa OK, Mobile, AL...
I mail to my cousin in Phoenix, AZ from NE Ohio and it's a zone 7 and to my brother in Houston and it's a zone 6. If I reuse a box and don't have to buy a new one I can send to my cousin without going over on postage. If you are mailing to zone 5 and 6 you can buy a box from Walmart and not go over on postage + box purchase for those hazmat shops. I always reuse boxes anyway. It's easy to get used boxes from the dollar store and then turn them inside out, tape them back up, and reuse them (save a tree).