For USPS Retail Ground™ (formerly Standard Post), the standard shipping is in 2-8 business days.
Other Mail & Shipping Services:
Priority Mail Express - Delivering 7 days a week, this is USPS fastest domestic service for time-sensitive letters, documents, or merchandise. Guaranteed overnight scheduled delivery to most locations2, including PO Boxes.
Priority Mail - Get more for your money with shipping in 1, 2, or 3 business days3 based on where your package starts and where it’s being sent.
First-Class Mail - Affordable mail service for standard-sized, single-piece envelopes weighing up to 3.5 oz, and large envelopes and small packages weighing up to 13 oz with delivery in 3 business days or less.
Tip! Here's A Customer's Guide to Mailing shared by Postal Explorer.