Word Per Minute (WPM) is calculated by calculating how many words you can type in one minute (5 characters/keystrokes Equals 1 word). The character per minute (CPM) rate is the number of characters typed each minute. CPM is more accurate and requires less time to measure than WPM. There are different ways to measure your typing speed. You can use a computerized system such as Kinex, WiKiSpeed, or TypingTest to get accurate results or you can simply record how many words you can type in one hour and divide that number by 60 to get your WPM. There are two main types of mechanical typewriters: single-unit models and multiple-unit models. Single-unit models have one key on the keyboard that forms each letter when pressed. To create a capital letter, for example, you would press the "Q" key then the "W" key. Multiple-unit models have several keys that form letters when they are pressed together. For example, the "q" key on a standard QWERTY keyboard will produce the letter "Q" if it is pressed alone. But if the "w" key is also pressed, the "q" will be replaced with a "W." Multiple-unit models are easier to operate but cannot reproduce every letter that can be typed on a single-unit model. For example, they cannot print the letter "J" because there is no key specifically designed to print this letter.