usps first class mail time estimate is a key factor when deciding which USPS service to use for your shipments. First-Class Mail typically delivers within one to five business days, with delivery speed depending on the origin and destination of the package. This makes First-Class Mail an ideal option for lightweight letters, documents, and small packages that don’t need to arrive immediately. USPS provides tracking for most First-Class Mail items, which allows senders to monitor the progress of their shipments. The time estimate can vary slightly based on factors such as weather conditions and local delivery schedules.