What is the maximum thickness allowed for a letter?

The maximum thickness allowed for a letter is 1/4 inches, which aligns with the USPS regulations for a standard letter. This specific thickness limit is crucial because it determines the physical characteristics of the mailpiece and affects the classification and postage rates. A letter that exceeds this thickness may be categorized as a flat, which incurs different postal rates and handling requirements.

Understanding the dimensions for mail is essential, as it ensures compliance with postal standards and can affect the delivery process. Letters must not only meet the thickness requirement but also adhere to other size constraints (length and width) to qualify for standard letter rates. It's important to familiarize yourself with these specifications to efficiently manage mail processing and ensure accurate postage applications.