Density Altitude Calculator
Density altitude is the pressure altitude corrected for non-standard temperature. It determines how your aircraft performs: the higher the density altitude, the thinner the air, and the more degraded your engine power, propeller thrust, and wing lift. This calculator uses the ICAO International Standard Atmosphere (ISA) as defined in ICAO Doc 7488. Enter your pressure altitude and the outside air temperature to compute density altitude in feet. A positive deviation above standard temperature raises density altitude above pressure altitude; a negative deviation lowers it.
Density altitude formula (ICAO ISA)
ISA Temp (°C) = 15 - (2 x PA / 1,000)
ISA Deviation = OAT - ISA Temp
Density Altitude (ft) = PA + (118.8 x ISA Deviation)
Where PA is pressure altitude in feet and OAT is outside air temperature in degrees Celsius. The factor 118.8 ft/°C is derived from the ISA standard lapse rate of 1.98°C per 1,000 ft. ICAO Doc 7488 defines the ISA lapse rate as 6.5 K/km in the troposphere.
Density altitude and aircraft performance
- Engine power: normally aspirated piston engines lose approximately 3% of rated power per 1,000 ft of density altitude increase.
- Takeoff roll: a rule of thumb is that takeoff distance increases roughly 10% per 1,000 ft of density altitude.
- Rate of climb: decreases proportionally with reduced available power and thrust.
- Service ceiling: the altitude at which rate of climb drops to 100 ft/min is significantly lower on high density altitude days.
- Never depart without computing density altitude. Hot, high, and humid conditions can make otherwise safe airports dangerous.
Density altitude calculator: frequently asked questions
What is density altitude?
Density altitude is the pressure altitude corrected for non-standard temperature. It represents the altitude in the ICAO standard atmosphere at which the air density equals the actual air density at your location. High density altitude means thinner air, which reduces aircraft engine power, propeller efficiency and wing lift.
How is density altitude calculated?
Using the ICAO standard atmosphere formula: DA = PA + (120 x (OAT - ISA_temp)), where PA is pressure altitude in feet, OAT is the outside air temperature in Celsius, and ISA_temp is the standard temperature at that pressure altitude (15C minus 2C per 1,000 ft). A more precise method uses: DA = PA + (118.8 x (OAT - ISA_temp)).
Why does density altitude matter for pilots?
High density altitude degrades aircraft performance. Takeoff and landing distances increase, rate of climb decreases, and engine power output drops. On hot days at high elevation airports, density altitude can exceed the airport elevation by thousands of feet, creating hazardous conditions that must be accounted for in pre-flight planning.
What is the ISA standard temperature at sea level?
The ICAO International Standard Atmosphere (ISA) defines sea-level temperature as 15 degrees Celsius (59 degrees Fahrenheit). Temperature decreases at the standard lapse rate of 1.98 degrees Celsius per 1,000 feet (approximately 2 degrees C per 1,000 ft) up to the tropopause at about 36,090 feet.
How does pressure altitude differ from density altitude?
Pressure altitude is the altitude indicated when the altimeter is set to the standard sea-level pressure of 1013.25 hPa (29.92 inHg). Density altitude is pressure altitude adjusted for actual temperature. When the temperature equals ISA standard temperature, pressure altitude equals density altitude. Above standard temperature, density altitude exceeds pressure altitude.
Official sources
- ICAO: Manual of the ICAO Standard Atmosphere, Doc 7488 (3rd ed.).
- FAA: Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25), Chapter 11: Weather Theory.
- NOAA: U.S. Standard Atmosphere 1976.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.