Handheld or tabletop timepieces to measure elapsed time between activation and deactivation points; analog or digital; may be shockproof, waterproof, and/or traceable; may have multiple functions; may include a neck cord or other attachment device.

A laboratory stopwatch measures time intervals using specific activation and deactivation points.

Analog or mechanical stopwatches are typically controlled by two buttons. The first button starts the timer and the second stops the measurement, and the elapsed time is displayed. The time can be re-started by pressing the first button again, and the time is reset to zero by pressing the second button again. The second button may also allow for lap times or split times.

Mechanical stopwatches are spring-powered and have to be wound periodically. Digital stopwatches and timers are usually powered by a silver cell or lithium battery.

Digital electronic stopwatches or timers have crystal oscillator timing elements that make them much more accurate than mechanical versions. They may also display the date and time. Some stopwatches count by centiseconds (1/100 of a second), which is not to be confused with milliseconds.

Digital timers are now available with a number of useful features. Some have more than one timing channel and can be used to simultaneously measure the time for more than a single activity.

All stopwatches and timers can be calibrated and certified based on standards traceable to the National Institute of Standards and Testing (NIST). Certified timepieces can then be used to calibrate other devices for everyday use.

Large digital stopwatches found in sports stadiums and that can be seen from a distance are called stopclocks. Stopwatch functions may also be available on wristwatches, cell phones, computers, and other electronic devices.