The airspeed indicator or airspeed gauge is an instrument used in an aircraft or vessel to display the speed, typically in knots, to the captain. The barometric airspeed indicator is now the standard design. The instrument consists of a pressure-tight housing to which the static pressure is connected. Inside the housing there is a barometric device (diaphragm unit), which is subjected to the total pressure of static and dynamic pressure.

The difference between total and static pressure corresponds to the Bernoulli equation the speed-dependent dynamic pressure. This pressure difference is shown on a scale as speed. When sailing and ultralight aircraft displaying the speed usually in km/h, however, takes place , with most aircraft and ships in knots, with some smaller schools and jets, mostly American manufacturer, in miles per hour. There are also airspeed indicator with several scales available.