Which tool is essential for weighing letter-sized mail?

A postal scale is a specialized tool designed to accurately determine the weight of letters and packages. This is crucial for mailing purposes because postal rates often depend on the weight of the item being sent. Using a postal scale allows mail clerks to ensure they affix the correct postage, which is vital for efficient mail processing and delivery.

In contrast, a digital thermometer measures temperature and is unrelated to mail handling. An electronic calculator, while useful for various numerical tasks, does not directly measure weight. A tape measure is used for measuring length or dimensions but not weight. Hence, the vital role of a postal scale in maintaining accurate mailing procedures establishes it as the essential tool for weighing letter-sized mail.