Calculate density altitude — pressure altitude corrected for temperature and humidity — to evaluate aircraft takeoff distance, climb performance, engine power loss, and dyno tuning parameters.
Quick Presets:
Enter the pressure altitude (altimeter set to 29.92 inHg) and outside air temperature. Density altitude reflects how the aircraft effectively behaves in flight.
Field elevation adjusted for non-standard altimeter setting.
Actual air temperature at the field, in Celsius.
Derive pressure altitude from the local altimeter setting and field elevation.
Current local altimeter setting. Standard is 29.92 inHg.
True airport elevation above sea level, in feet.
Actual air temperature at the field, in Celsius.
Compare actual temperature against the International Standard Atmosphere (ISA) baseline (15°C at sea level, −2°C per 1,000 ft).
Pressure altitude to compare against the standard atmosphere.
Actual air temperature at that altitude, in Celsius.
Advanced Parameters & Atmosphere Model
Moist air is less dense than dry air. High humidity adds to effective density altitude.
Exact ICAO uses ideal gas equations ($\rho = P/RT$); Pilot rule uses the 120 ft per °C approximation.
Result
Low Impact
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Enter pressure altitude and outside air temperature to compute density altitude.
0 ft3,000 (Low)6,000 (Mod)9,000 (High)12,000+ ft
Pressure Alt—
OAT—
ISA Temp—
ISA Deviation—
Air Density (σ)—
Engine HP Output—
Takeoff Ground Roll—
Dyno Correction (CF)—
4 min read3 steps7 terms3 examples6 FAQsDA = PA + 120 × (OAT − ISA_temp)
Density altitude tells pilots how an aircraft will actually perform, independent of what the altimeter or a sea-level chart says.
On the Density Altitude tab, enter the pressure altitude (PA) — field elevation adjusted for the altimeter setting — and the outside air temperature (OAT) in Celsius. Don't have pressure altitude handy? Switch to the From Altimeter tab and enter the altimeter setting and field elevation instead; the calculator derives PA for you. The result updates instantly as you type.
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Read the density altitude and performance note
The result card shows density altitude (DA) in feet, the ISA deviation (how much warmer or cooler than standard the air is), and a plain-language performance note. A higher DA means the aircraft behaves as if it were flying from a higher, thinner-air airport — longer takeoff rolls, reduced climb rate, and less propeller and engine efficiency.
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Check the ISA reference
Use the ISA Deviation tab to see the International Standard Atmosphere temperature at any altitude and how far today's actual temperature departs from it. A positive deviation (warmer than ISA) always raises density altitude above pressure altitude; a negative deviation lowers it.
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Reference
Formula & Methodology
3 formulas▸
Density altitude
DA = PA + 120 × (OAT − ISA_temp)
Density altitude (DA) is the pressure altitude (PA) corrected for how far the actual outside air temperature (OAT) departs from the International Standard Atmosphere (ISA) temperature predicted for that altitude. Each degree Celsius above ISA adds about 120 ft to density altitude; each degree below subtracts about 120 ft. Both PA and DA are in feet; OAT and ISA temperature are in Celsius.
ISA standard temperature
ISA_temp = 15 − 2 × (altitude / 1000)
The International Standard Atmosphere defines sea-level temperature as 15°C, falling by 2°C for every 1,000 ft of altitude in the troposphere. This is the reference temperature that OAT is compared against — the ISA deviation is simply OAT minus this value.
Pressure altitude from altimeter setting
PA = field elevation + (29.92 − altimeter setting) × 1000
Pressure altitude is the altitude the altimeter would read if set to the standard sea-level pressure of 29.92 inHg. When the local altimeter setting is below standard, the true pressure altitude is higher than field elevation; when it's above standard, PA is lower.
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General reference
Trust, Methodology & Sources
Written by Calculover Editorial Team · Updated 2026-07-31 · 3 sources▸
Editorial accountability
Author: Calculover Editorial Team - Editor
Owner: Calculover Editorial Team - Editorial owner
Last reviewed: 2026-07-31
Last verified: 2026-07-31
Methodology
This Density Altitude Calculator is modeled after the 1976 U.S. Standard Atmosphere and ICAO Standard Atmosphere (Doc 7488) specifications. Pressure altitude and temperature deviation formulas conform to FAA flight training standards in the Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25C).
Limitations & guidance
Professional guidance: This tool is provided for educational, reference, and pre-flight planning estimation only. It is not a substitute for your aircraft's official Pilot's Operating Handbook (POH) or Airplane Flight Manual (AFM) performance charts. Pilots-in-command maintain sole responsibility for verifying takeoff and landing performance requirements prior to flight.
Density altitude (DA) ↗Pressure altitude corrected for non-standard temperature — the altitude in the standard atmosphere that would produce the air density actually present. Used to estimate real-world aircraft and engine performance.
Pressure altitude (PA) ↗The altitude indicated when an altimeter is set to 29.92 inHg (standard sea-level pressure), regardless of the local altimeter setting or field elevation.
ISA (International Standard Atmosphere) ↗A standardized model atmosphere defining sea-level temperature (15°C), pressure (29.92 inHg), and how both change with altitude. It's the baseline every actual day's weather is compared against.
Standard atmosphere ↗Another name for the ISA model — the reference conditions (temperature falling 2°C per 1,000 ft) used to define both pressure altitude and density altitude.
Altimeter setting ↗The local barometric pressure, in inches of mercury (inHg), that pilots dial into an altimeter so it reads true altitude above sea level. Standard is 29.92 inHg.
Aircraft performance ↗Takeoff distance, climb rate, service ceiling, and engine/propeller efficiency — all of which degrade as density altitude rises, since thinner air produces less lift and less power.
High, hot, and heavy ↗Pilot shorthand for the worst-case density-altitude scenario: a high-elevation airport, hot temperatures, and a heavily loaded aircraft, all of which compound to reduce performance.
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Scenarios
Real-World Examples
3 worked examples▸
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Hot-day departure
5,000 ft pressure altitude on a hot afternoon
Pressure altitude 5,000 ftOutside air temperature 30°C
ISA temperature at 5,000 ft is 15 − 2×5 = 5°C, so the ISA deviation is 30 − 5 = +25°C. DA = 5,000 + 120×25 = 8,000 ft — the aircraft performs as though departing from an 8,000 ft airport on a standard day, well into the range where takeoff roll and climb performance are meaningfully degraded.
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Deriving pressure altitude from the altimeter
3,000 ft field elevation, non-standard altimeter setting
Field elevation 3,000 ftAltimeter setting 29.72 inHgOutside air temperature 25°C
PA = 3,000 + (29.92 − 29.72)×1,000 = 3,200 ft. ISA temp at 3,200 ft is 15 − 2×3.2 = 8.6°C, so the deviation is 25 − 8.6 = +16.4°C, giving DA = 3,200 + 120×16.4 ≈ 5,168 ft — noticeably higher than the field elevation alone would suggest.
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Reading an ISA deviation
How far off standard is today's temperature?
Altitude 5,000 ftOutside air temperature 30°C
The standard ISA temperature at 5,000 ft is 5°C. Today's 30°C is +25°C above standard — a large positive deviation that alone accounts for the full 3,000 ft gap between pressure altitude and density altitude in this scenario.
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Reference
Cite This Calculator
APA & MLA▸
Use either format to cite this calculator in a paper, report, or resource list.
Density altitude tells pilots how an aircraft will actually perform, independent of what the altimeter or a sea-level chart says. It's the single number that folds together elevation, barometric pressure, and temperature into the altitude the airplane effectively "feels" — critical for planning safe takeoffs, climbs, and landings, especially at high-elevation or hot-weather airports.
How the Density Altitude Calculator works
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Density altitude is computed as DA = PA + 120 × (OAT − ISA_temp), where PA is pressure altitude in feet, OAT is the actual outside air temperature in Celsius, and ISA_temp is the International Standard Atmosphere's predicted temperature at that pressure altitude (15°C at sea level, falling 2°C per 1,000 ft). The 120 ft-per-degree factor approximates how much air density — and therefore lift, thrust, and propeller efficiency — changes per degree of temperature deviation from standard.
When the air is warmer than ISA predicts (a positive deviation), it's less dense, so density altitude rises above pressure altitude — the aircraft behaves as if it were at a higher, thinner-air altitude. When the air is cooler than standard, density altitude drops below pressure altitude and performance improves.
Inputs and what they mean
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The Density Altitude tab needs pressure altitude (PA, in feet) and outside air temperature (OAT, in Celsius). If you only know your field elevation and the current altimeter setting, use the From Altimeter tab instead: PA = field elevation + (29.92 − altimeter setting) × 1,000, since altimeter settings below the 29.92 inHg standard indicate lower atmospheric pressure and therefore a higher true pressure altitude than the field elevation alone suggests.
The ISA Deviation tab is a reference tool — enter any altitude and temperature to see the standard ISA temperature at that altitude and how far today's actual temperature departs from it. That deviation, multiplied by 120 ft per degree, is exactly the correction applied to pressure altitude to get density altitude.
Limits and edge cases
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This calculator uses the standard 120 ft-per-degree Celsius rule of thumb, which is accurate enough for flight planning but is an approximation — exact density altitude also depends slightly on humidity (humid air is less dense than dry air at the same temperature and pressure), which this tool doesn't model. For precise performance planning, always cross-check the result against your aircraft's POH (Pilot's Operating Handbook) performance charts, which account for the airplane's specific weight, configuration, and engine characteristics. Extremely high or low temperature inputs (well outside normal atmospheric ranges) will still compute a mathematically valid result, but the 120 ft/°C approximation grows less reliable far from typical conditions.
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Questions
Frequently Asked Questions
6 questions▸
What is the formula for density altitude?+
DA = PA + 120 × (OAT − ISA temperature), where PA is pressure altitude in feet, OAT is the actual outside air temperature in Celsius, and ISA temperature is the standard-atmosphere temperature predicted for that altitude (15°C at sea level, minus 2°C per 1,000 ft).
Why does density altitude matter for aircraft performance?+
Higher density altitude means thinner air, which reduces lift from the wings, thrust from the propeller or engine, and overall aircraft performance. Pilots use density altitude to predict longer takeoff rolls, slower climb rates, and reduced service ceiling compared to standard-day conditions.
What does a high density altitude mean in practice?+
A high density altitude means less lift and less engine/propeller power than the field elevation alone would suggest — the aircraft performs as though it were taking off from a much higher airport. This is the core of the "high, hot, and heavy" hazard pilots are trained to respect.
What is the International Standard Atmosphere (ISA)?+
ISA is a reference model atmosphere defining sea-level temperature (15°C) and pressure (29.92 inHg), with temperature falling 2°C per 1,000 ft of altitude. It's the baseline every real-world temperature and pressure reading is compared against to compute deviations.
What is the standard altimeter setting?+
29.92 inches of mercury (inHg) is the standard sea-level pressure altimeters are set to when computing pressure altitude, regardless of the actual local barometric pressure.
What units does this calculator use?+
Pressure altitude and density altitude are in feet, outside air temperature and ISA temperature are in Celsius, altimeter setting is in inches of mercury (inHg), and field elevation is in feet.
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