Density Altitude Calculator
Density altitude calculator. Finds pressure altitude and density altitude from field elevation, altimeter setting and temperature for aircraft performance. Educational.
Density Altitude Calculator
How to use the density altitude calculator
Enter the field elevation
Type the airport or field elevation in feet above mean sea level — the value printed on the chart or in the airport directory.
Enter the altimeter setting
Use the current altimeter setting in inches of mercury (from ATIS or the nearest station). Leave it at 29.92 for the standard value if you only want a temperature effect.
Enter the temperature
Type the outside air temperature in Celsius. Heat is the biggest driver of high density altitude, so accuracy here matters most.
Read the result
You get the density altitude, the pressure altitude, and how far the temperature is from standard. Use it to anticipate reduced performance — but plan from your aircraft's POH, not this estimate.
Density altitude — the altitude the aircraft really feels
Thin air, weak performance
An aircraft's wings, propeller, and engine all depend on the density of the air, and density falls as air gets higher, hotter, or more humid. Density altitude is the single number that captures this: it is the altitude in the standard atmosphere at which the air density equals the density you actually have. On a hot day at a high-elevation airport, the air can be as thin as it would be thousands of feet higher in standard conditions, and the aircraft performs accordingly — longer takeoff rolls, shallower climb, reduced engine power, and less propeller thrust. Pilots get there in two steps. First they find the pressure altitude, the altitude shown when the altimeter is set to the standard 29.92 inches of mercury; it equals the field elevation plus about a thousand feet for every inch the actual setting is below standard. Then they correct for temperature: for every degree the air is warmer than the standard (ISA) temperature at that pressure altitude, density altitude rises by roughly 120 feet. The familiar rule of thumb is density altitude equals pressure altitude plus 120 times the temperature deviation from standard.
The temperature term usually dominates. Standard temperature at sea level is 15 °C, falling about 2 °C per thousand feet, so on a 35 °C summer day at a 5,000-foot airport the air behaves like roughly 8,000 feet — a big penalty for a small aircraft. This is why density altitude is a recurring factor in mountain and summer flying accidents: the runway looks long enough and the air feels fine, but the aircraft simply cannot climb the way the pilot expects.
"Density altitude is why a hot, high airport can humble an aircraft that performs fine at sea level. The wing doesn't care about your elevation — only about how thin the air is, and heat thins it fast."
An estimate, not a flight plan
This calculator uses the standard pilot approximations — pressure altitude from the altimeter setting and the 120-feet-per-degree temperature rule — which are what flight training teaches and an E6B computes. They are good enough to build awareness and to sense how conditions are trending, but they are approximations: the 120-feet figure is most accurate near sea level and drifts at higher altitudes, and the simple model ignores humidity, which raises density altitude further on muggy days (water vapour is lighter than dry air). Crucially, density altitude tells you the environment, not your aircraft's actual numbers. The takeoff distance, climb rate, and service ceiling for your specific aircraft at a given density altitude come from the performance charts in its Pilot's Operating Handbook, applied with the correct weight, runway surface, slope, and wind — and with a healthy safety margin. Treat the value here as an educational estimate and a planning prompt; never substitute it for the POH, an approved E6B, current weather, and your own pre-flight performance calculation. Real go/no-go decisions are the pilot's, made from official data.
10 Facts About Density Altitude
Density altitude = the altitude the air density matches.
Air thins with height, heat, and humidity.
High DA means longer takeoffs, weaker climb.
Pressure altitude = elevation + (29.92 − setting)×1000.
Rule of thumb: +120 ft per °C above standard.
Standard temp is 15 °C, −2 °C per 1,000 ft.
Temperature usually dominates the result.
Humidity raises DA further (not in the basic rule).
A factor in many mountain and summer accidents.
Use the POH for actual aircraft performance.
Frequently asked questions
It's the altitude in the standard atmosphere at which the air density equals the density you currently have. Because aircraft performance depends on air density, density altitude tells you how the aircraft will perform: a high density altitude means thin air and degraded takeoff, climb, and engine performance. It rises with elevation, temperature, and humidity — so a hot day at a high airport produces a density altitude well above the field elevation.
First find pressure altitude: field elevation plus about 1,000 feet for each inch of mercury the altimeter setting is below the standard 29.92. Then correct for temperature using the rule of thumb that density altitude rises about 120 feet for every degree Celsius the air is warmer than the standard temperature at that pressure altitude (15 °C at sea level, falling about 2 °C per thousand feet). The calculator does both steps from your inputs.
Thin air reduces the lift the wings produce, the thrust the propeller generates, and the power the engine makes, all at once. The result is a longer takeoff roll, a slower acceleration, and a much shallower climb. A runway and obstacle clearance that are comfortable on a cool day at sea level can become marginal — or impossible — at a high density altitude. That's why density altitude is a central consideration in hot-and-high operations and a recurring theme in accident reports.
Pressure altitude is what the altimeter reads with the standard setting (29.92) — it accounts for the pressure but assumes standard temperature. Density altitude is pressure altitude corrected for the actual (non-standard) temperature, so it reflects the true air density. On a standard-temperature day they're equal; on a hot day the density altitude is higher than the pressure altitude. Performance depends on density altitude, which is why the temperature correction is essential.
Yes. Water vapour is less dense than dry air, so humid air is thinner than dry air at the same temperature and pressure, which raises density altitude and further degrades performance. The standard pilot rule of thumb used here ignores humidity, so on a hot, humid day the true density altitude is a little higher than this calculator shows. Some advanced calculators include a humidity term; treat the result here as a dry-air estimate to be taken conservatively.
It's a good approximation that flight training and the E6B use, most accurate at lower altitudes and drifting slightly at higher ones, where the true factor is a bit larger. For awareness and planning it's perfectly serviceable. For precise performance numbers, however, you don't use density altitude directly — you read your aircraft's takeoff and climb charts in the Pilot's Operating Handbook at the computed density altitude, which already bake in the exact relationships.
The current local setting from ATIS, AWOS, or the nearest reporting station, in inches of mercury. If you only want to see the temperature effect at standard pressure, leave it at 29.92, which makes pressure altitude equal to field elevation. In regions that report pressure in hectopascals (millibars), convert first or use a setting in inHg, since this calculator expects inches of mercury.
Use it to build awareness and to anticipate when density altitude will be a factor, but not as your planning source. Actual takeoff distance, climb rate, and obstacle clearance must come from your aircraft's POH performance charts at the computed density altitude, applied with the real weight, runway, slope, wind, and a safety margin — and using current official weather, not an estimate. The pilot is responsible for the go/no-go decision based on approved data.
There's no single threshold — it depends on the aircraft, its weight, and the runway — but performance degrades noticeably once density altitude climbs a couple of thousand feet above the field elevation, and many light aircraft struggle markedly above about 7,000–8,000 feet of density altitude, especially heavily loaded. Mountain airports on hot days routinely exceed that. The right question isn't a fixed number but whether your aircraft's POH still gives adequate takeoff distance and climb at the computed density altitude and weight, with margin.
No. The values you enter are processed entirely in your browser. Nothing is sent to a server, stored, or shared, and no account is required. The calculation runs on your device only.
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