Density Altitude Calculator

Enter field elevation, altimeter setting, and outside air temperature to calculate density altitude — the altitude at which your aircraft's engine, propeller, and wings actually perform.

Quick Facts

Pressure altitude
PA = Elevation + (29.92 − Altimeter) × 1,000
Adjusts field elevation for the current barometric pressure.
Density altitude
DA = PA + 120 × (OAT − ISA Temp)
Standard FAA/NWS quick-reference formula (temperatures in °C).
ISA baseline
15°C at sea level, −2°C per 1,000 ft
Standard atmosphere temperature used as the reference.
Rule of thumb
≈1,000 ft DA per 10°F above standard
Higher density altitude means thinner air — less lift and power.

Your Results

Calculated
Density Altitude
-
Effective altitude the aircraft "feels"
Pressure Altitude
-
PA = Elevation + (29.92 − Altimeter) × 1,000
ISA Temperature at PA
-
Standard temperature expected at that pressure altitude
DA Above Field Elevation
-
How much "higher" the aircraft performs as if flying

Ready

Enter field elevation, altimeter setting, and temperature, then press Calculate.

Formula and Method for Density Altitude

Density altitude is pressure altitude corrected for non-standard temperature — the altitude in the International Standard Atmosphere (ISA) at which the current air actually has the density you're flying in. Air density governs how much lift a wing generates, how much thrust an engine and propeller (or rotor) produce, and how quickly an aircraft accelerates down the runway, so pilots use density altitude, not raw field elevation, to judge real-world performance. On a hot afternoon at a high-elevation airport, density altitude can run thousands of feet above the field's charted elevation, meaning the aircraft performs as if it were taking off from a much higher, thinner-air field.

How the calculation works

This calculator uses the FAA/National Weather Service quick-reference method. First it finds pressure altitude: PA = Field Elevation + (29.92 − Altimeter Setting) × 1,000, which adjusts elevation for the current barometric pressure — each inHg below the standard 29.92 inHg adds about 1,000 ft to pressure altitude, and each inHg above subtracts about 1,000 ft. Next it finds the standard (ISA) temperature expected at that pressure altitude: ISA Temp = 15°C − (2°C × PA / 1,000), based on the standard atmosphere's 15°C sea-level temperature and its roughly 2°C-per-1,000-ft lapse rate. Finally it applies the correction: Density Altitude = PA + 120 × (OAT − ISA Temp), where OAT is the actual outside air temperature in Celsius. Every degree Celsius the air is warmer than standard adds about 120 ft of density altitude; every degree colder subtracts about 120 ft.

Common mistakes

  • Confusing density altitude with field elevation: a 1,500 ft airport on a hot afternoon can have a density altitude over 4,000 ft — performance planning must use density altitude, not the airport's charted elevation.
  • Entering station pressure instead of altimeter setting: the altimeter setting is pressure already adjusted to sea level; using raw, unadjusted station pressure throws off the pressure-altitude calculation.
  • Mixing up temperature units: the formula works in Celsius internally — confusing a Fahrenheit reading for Celsius (or vice versa) can shift the result by thousands of feet.
  • Ignoring humidity on muggy days: this formula captures temperature and pressure, which dominate the effect; high humidity adds a further, usually smaller, increase in true density altitude that pilots account for separately.

Why pilots track density altitude

  • Preflight planning: comparing density altitude to an aircraft's takeoff- and climb-performance charts to confirm runway length and obstacle clearance are adequate.
  • Weight and load decisions: trimming fuel, passengers, or cargo on hot, high-elevation, or humid days when density altitude erodes climb performance.
  • Helicopter operations: rotorcraft hover performance (especially out-of-ground-effect) is highly sensitive to density altitude.
  • Airport advisories: many high-elevation airports post current density altitude so pilots can judge conditions before engine start.

Frequently Asked Questions

What is density altitude?
Density altitude is pressure altitude corrected for temperature — the altitude in the standard atmosphere at which the surrounding air would have the same density as the air you are actually flying in. It expresses how thin the air feels to an aircraft, independent of the field's actual elevation.
How do you calculate density altitude?
First find pressure altitude: PA = elevation + (29.92 − altimeter setting) × 1,000. Then find the standard (ISA) temperature at that pressure altitude: 15°C − (2°C × PA/1,000). Finally, Density Altitude = PA + 120 × (actual temperature − ISA temperature), with temperatures in Celsius.
Why does density altitude matter for flying?
Higher density altitude means thinner air: engines produce less power, propellers and rotors bite less air, and wings generate less lift at a given airspeed. That lengthens takeoff and landing rolls, reduces climb rate, and can significantly cut useful load, especially at high-elevation airports in hot weather.
Does humidity affect density altitude?
Yes, but the effect is smaller than temperature and pressure. Moist air is less dense than dry air at the same temperature and pressure because water vapor molecules are lighter than nitrogen and oxygen molecules. This calculator uses the standard FAA/NWS temperature-and-pressure formula; on very humid days the true density altitude will be somewhat higher than the value shown.

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