Density Altitude Calculator — Aviation Performance
Calculate density altitude — the key metric for aircraft takeoff and climb performance — from field elevation, altimeter setting and outside air temperature.
ft
inHg
°C
The altitude the atmosphere behaves like for aircraft performance — higher means less thrust and lift
- 1
Pressure altitude
1,000 + 1000 × (29.92 − 29.92) = 1,000Each 0.01 inHg departure from the standard 29.92 inHg shifts pressure altitude by ~10 ft. - 2
ISA temperature at PA
15 − 0.00198 × 1,000 = 13 - 3
ISA deviation
25 − 13 = 12 - 4
Density altitude
1,000 + 120 × 12 = 2,438
How does this calculator work?
Density altitude ≈ pressure altitude + 120 × (OAT − ISA_temp). Pressure altitude = field elevation + 1 000 × (29.92 − QNH_inHg). At 5 000 ft with 29.92 inHg and OAT 35°C (15°C above ISA), DA ≈ 5 000 + 120 × 15 = 6 800 ft. Higher DA means degraded takeoff and climb performance.
Formula
How this is calculated
Air density determines how much lift a wing generates and how much power an engine produces. Density decreases with altitude, temperature and humidity. Density altitude (DA) is the altitude in the International Standard Atmosphere (ISA) that has the same density as your current conditions — so a hot, high-altitude airport behaves as if it were at a higher ISA altitude. The calculation uses editable estimates based on ICAO 2026 standard atmosphere values.
The calculation is two steps. First, pressure altitude (PA) corrects the field elevation for non-standard barometric pressure: PA = elevation + 1 000 × (29.92 − QNH_inHg). Each 0.01 inHg departure from the standard 29.92 inHg shifts PA by about 10 ft. Second, density altitude applies the temperature correction: DA ≈ PA + 120 × ISA_deviation, where ISA_deviation = OAT − (15 − 0.00198 × PA). The coefficient 120 ft/°C is the standard FAA/ICAO aviation approximation; a more precise integration of the barometric formula changes the result by at most a few hundred feet within the troposphere.
A positive ISA deviation (warmer than standard) raises density altitude — runway performance degrades and climb rates fall. At 'hot and high' airports like Quito (9 228 ft, often 20°C above ISA) or Addis Ababa (7 625 ft), density altitudes can exceed 11 000 ft even on the ground. Humidity adds a small further penalty (moist air is slightly less dense than dry) not captured in this formula — add 50–100 ft on a hot, humid day as a rule of thumb.
Frequently asked questions
Less dense air means a wing must move faster to produce the same lift, lengthening takeoff and landing rolls. Engines also ingest less oxygen mass per intake stroke, reducing power output by roughly 3% per 1 000 ft of density altitude for naturally aspirated piston engines. Turbocharged engines maintain sea-level power to their critical altitude but still lose lift efficiency.
29.92 inHg (1013.25 hPa) is the ICAO standard sea-level pressure. If you enter 29.92, pressure altitude equals field elevation — correct for standard conditions. For planning at a specific airport, enter today's QNH from the ATIS or METAR to correct for actual barometric pressure.
No — like the standard ICAO formula, this uses dry-air density. Humid air is about 0.5–1.5% less dense than dry air at the same conditions. On a hot, humid day add roughly 50–100 ft to the density altitude result as a conservative margin.
Also known as
TG we-Calculate Editorial Team. (2026). Density Altitude Calculator — Aviation Performance [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/density-altitude-calculator
TG we-Calculate Editorial Team. "Density Altitude Calculator — Aviation Performance." TG we-Calculate. 2026. https://we-calculate.com/calculator/density-altitude-calculator.
TG we-Calculate Editorial Team, "Density Altitude Calculator — Aviation Performance," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/density-altitude-calculator
@misc{wecalculate_density_altitude_calculator, title = {Density Altitude Calculator — Aviation Performance}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/density-altitude-calculator}}, year = {2026}, note = {TG we-Calculate} }
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