Here are the cheapest ways to ship with USPS:
1- If your package weighs less than 15.9 ounces, USPS First Class Shipping services will probably be the cheapest option.
2- If it weighs more than 1 lb and fits into a flat rate priority envelope or box then this will be your next cheapest option.
3- If you have a package that weighs 1-20 lbs and does not fit in a flat rate envelope or box, you will want to ship with USPS priority cubic services. Find the smallest box you can fit your item in and use cubic. As long as your item doesn’t exceed the cubic dimensions then use this! If you are using other carriers to ship boxes this size, you will save A LOT of money by using USPS priority cubic! Cubic is generally only offered to companies that ship extremely high volume, but we level the playing field and offer it to anyone! For more information on Cubic check out our blog post “Cubic Shipping”.
4- Anything over 20 lbs you’d want to go with medium to large flat rate boxes, but only use those if it is over 20 lbs. Under 20 lbs, cubic will generally be cheaper.