The United States Postal Service offers five classes, or services, of mail distribution based on size, shape, weight and delivery time. With two of those services, first-class and priority mail, the USPS handles items ranging from postcards to 70-pound packages. You can use both for documents, correspondence and packages weighing less than 13 ounces; the postal service considers anything larger or heavier to be priority mail. The similarities end, however, when you consider delivery time, cost and optional services.
Business and personal correspondence such as greeting cards, large envelopes, letters, postcards and small packages weighing less than 13 ounces typically arrive in their intended mailboxes by first-class mail. Priority mail is also an option for these first-class pieces. However, letters, envelopes and packages weighing between 13 ounces and 70 pounds, envelopes larger than 15 by 12 inches and tubes fall under the priority mail class. Priority mail flat rate containers range in size from 6-by-10-inch envelopes to 14-inch boxes.
Both first-class and priority mail have a one- to three-day delivery window for domestic addresses. The postal zones traveled determine one-day, two-day or three-day priority mail delivery. First-class international delivery varies by destination, according to the postal service, while international priority mail to any of 180 countries takes six to eight business days. Neither service carries a guaranteed delivery date or specific delivery time frame.
The USPS periodically raises postal rates in line with inflation, but customers typically spend less for first-class delivery than priority mail, as the latter's fees are distance-based. As of publication, a 9-by-12-inch envelope weighing 13 ounces, mailed first-class in Pittsburgh on Wednesday, would arrive across Pennsylvania in Philadelphia two days later and cost the sender $3.50, according to the USPS Postage Calculator. That same envelope sent priority mail two-day would cost $5.85, or $5.75 using the priority mail envelope flat rate, as of publication. A 13-ounce package would cost $4.12 via first class, $5.85 via priority mail two-day or $5.95 priority mail small box flat rate box.
Although priority mail costs more than first class, USPS includes free tracking, free pickup and a maximum of $50 in insurance at no charge. Forwarding and return service are also no-cost features. Special priority mail boxes, labels and envelopes are free at any post office or shipped free to your home or business when ordered online through the USPS store. First-class mail options, such as forwarding, address correction and tracking, must all be purchased. Both services can include delivery confirmation, proof of mailing and protection against loss or damage at an extra cost.