Density Altitude Calculator
Find density altitude from field elevation, altimeter setting, and outside air temperature, with a plain-language pilot performance note.
🌡️ What is Density Altitude?
Density altitude is pressure altitude corrected for non-standard temperature, it is the altitude in the International Standard Atmosphere (ISA) that would produce the same air density as the actual local conditions. Because air density directly determines how much power an engine can produce, how efficiently a propeller bites the air, and how much lift a wing generates, density altitude is the single number pilots use to judge how the air will actually "feel" to the aircraft, regardless of what the field elevation sign says.
Pilots and flight planners check density altitude before nearly every flight, to estimate takeoff roll and climb performance accurately, especially at high-elevation or backcountry airports, to recognize the dangerous "hot and high" combination where high field elevation and high temperature stack together to erode performance far beyond what field elevation alone would suggest, to decide whether a loaded aircraft can safely clear obstacles on departure, and to understand why the same airplane performs noticeably differently at the same airport on a cold winter morning versus a hot summer afternoon.
A common misconception is that density altitude only matters at high-elevation mountain airports. In reality, a low-elevation airport on an unusually hot day can also reach a meaningfully elevated density altitude, since temperature, not just elevation, drives the correction. Density altitude can also come out below field elevation on a cold day, meaning better-than-standard performance, it is not a one-directional penalty.
This calculator computes pressure altitude internally from field elevation and altimeter setting using the standard FAA formula, then applies the ISA lapse rate (15°C at sea level, decreasing 1.98°C per 1000 ft of pressure altitude) to find density altitude, and adds a plain-language note on how much aircraft performance is likely to be affected.
📐 Formula
Per the FAA Pilot's Handbook of Aeronautical Knowledge, this two-step calculation (pressure altitude, then ISA temperature correction) is the standard method for finding density altitude.
📖 How to Use This Calculator
Steps
💡 Example Calculations
Example 1 — Hot and High Airport
Field elevation = 5000 ft, altimeter = 29.92 inHg, OAT = 35°C
Example 2 — Standard Day at Sea Level
Field elevation = 0 ft, altimeter = 29.92 inHg, OAT = 15°C
Example 3 — Cold Day, Better Than Standard
Field elevation = 3000 ft, altimeter = 30.10 inHg, OAT = -5°C
❓ Frequently Asked Questions
🔗 Related Calculators
What is density altitude?
Density altitude is pressure altitude corrected for non-standard temperature. It represents the altitude in the standard atmosphere that would have the same air density as the actual conditions, and it directly affects engine power, propeller efficiency, and wing lift.
How do you calculate density altitude?
DA (ft) = PA (ft) + 120 x (OAT in degrees C - ISA standard temperature at PA in degrees C). Pressure altitude (PA) is computed first from field elevation and altimeter setting, then compared to the standard ISA temperature at that pressure altitude.
What is the ISA standard temperature formula?
The International Standard Atmosphere (ISA) temperature at a given pressure altitude is 15 degrees C minus 1.98 degrees C for every 1000 ft of pressure altitude: T_ISA = 15 - 1.98 x (PA / 1000).
Why is density altitude important for pilots?
Density altitude directly affects takeoff roll, climb rate, and service ceiling. High density altitude, from hot temperatures, high elevation, or both, means thinner air, meaning less engine power, less propeller thrust, and less lift, which can significantly lengthen takeoff distance and reduce climb performance.
What is a 'hot and high' airport?
A 'hot and high' airport combines high field elevation with high outside air temperature, both of which push density altitude well above field elevation. This combination is a well known hazard in aviation, since it can silently erode aircraft performance far more than pilots expect from field elevation alone.
Does this calculator require pressure altitude as a separate input?
No. This calculator accepts field elevation and altimeter setting directly and computes pressure altitude internally using the same formula as the Pressure Altitude Calculator, then applies the ISA lapse rate to derive density altitude, so you do not need to calculate pressure altitude separately first.
Can density altitude be lower than field elevation?
Yes. On a cold day, when the outside air temperature is below the ISA standard temperature for that pressure altitude, density altitude comes out below pressure altitude (and often below field elevation too), meaning better-than-standard aircraft performance.
How much does density altitude affect takeoff distance?
The exact effect depends on the specific aircraft's performance charts, but as a rule of thumb, every roughly 1000 ft increase in density altitude noticeably lengthens takeoff roll and reduces climb rate, effects that compound quickly at density altitudes several thousand feet above field elevation.
What temperature unit does this calculator use?
Outside air temperature (OAT) is entered in degrees Celsius, matching the ISA standard atmosphere convention used throughout the density altitude formula.
Is density altitude the same everywhere on a given day?
No. Density altitude depends on local field elevation, local altimeter setting, and local outside air temperature, all three vary by location, so density altitude must be computed separately for each airport and each set of current conditions.