The airspeed indicator in aircraft design measures the speed of the aircraft through the air. The formula to calculate indicated airspeed (IAS) is:
- IAS is the indicated airspeed (in knots or other airspeed units).
- P is the dynamic pressure (in pascals or pounds per square foot), which is usually obtained from the pitot-static system.
- ρ (rho) is the air density (in kilograms per cubic meter or slugs per cubic foot), which is influenced by altitude and temperature.