A letter scale, sometimes called a postage scale or postal scale, weighs mail in order to determine the exact amount of postage required. Letter scales are available with a variety of features for business or personal use. Especially when combined with a postage meter, a letter scale can save money on postage and cut down on the amount of human labor needed to post mail accurately.
There are two basic types of letter scales: manual and digital. Manual scales, also called mechanical scales, are typically less expensive, but they require the user to read the weight from a mechanical needle. They might also require periodic manual recalibration.
Digital, or electronic, letter scales have gained popularity since the 1990s. These give a digital reading, reducing the likelihood of human error. Some also automatically calculate the amount of postage required using rates downloaded from the Internet.
To calculate the amount of postage required, the user can weigh the letter on the scale. He or she can find the current rate for postal mail and calculate the cost accordingly. For example, in the United States in 2011, the rate for first-class domestic mail was $0.44 US Dollars (USD) for the first ounce (28.3 g), then $0.17 USD for each ounce (28.3 g) after that. Based on these rates, a 3-ounce (85-gram) letter would require $0.78 USD in postage.
Using this method to calculate postage can save the user money by preventing him or her from overestimating the amount of postage needed. For instance, someone mailing a 3-ounce (85-gram) letter might know that it is too heavy for a single $0.44 USD stamp and put two stamps on the package, for a total of $0.88 USD in postage. Using a letter scale to get the actual measurement would save $0.10 USD in this case.
For home or low-volume business use, a simple letter scale is generally sufficient, but some businesses might benefit from scales that have additional features. Larger models are available that can weigh bulk mail or heavy packages. Most industrial scales easily hook up to a postal meter, which automatically calculates and prints or stamps the appropriate amount of postage, eliminating the need to look up and calculate postage rates. The postal service might then charge the company based on the amount of postage used in a given month. Other models might compare the prices of various commercial mail carriers to find the best rate or calculate the rates for different classes of mail delivery.