Density Altitude Calculator
Compute density altitude from field elevation, altimeter setting, and outside air temperature (OAT). Density altitude (DA) is the altitude at which the standard atmosphere has the same density as your current conditions. Higher DA = lower power available, longer takeoff/landing distance, lower hover ceiling.
Calculator inputs and results
Field conditions
Optional
Note: dewpoint affects true density slightly (humid air is less dense than dry air at the same temperature and pressure) but the standard FAA density altitude formula does not include dewpoint. This calculator uses the standard FAA formula.
Density altitude formula per FAA-H-8083-25B (Pilot Handbook of Aeronautical Knowledge): DA = PA + 120 × (OAT - ISA). Rule of thumb for power loss: ~3% per 1,000 ft DA. Always verify with your aircraft Pilot Operating Handbook hover/climb performance charts.
How this calculator works
Pressure altitude (PA) = field elevation + (29.92 - altimeter setting in inches Hg) x 1,000. This converts your indicated altitude reference to the standard atmosphere reference.
Density altitude (DA) = PA + 120 x (OAT - ISA temperature at PA). ISA temperature at PA = 15°C - (PA / 1,000) x 2°C. This is the formula published in FAA-H-8083-25B Pilot's Handbook of Aeronautical Knowledge.
Rule of thumb for hover power loss: approximately 3% per 1,000 feet of density altitude. At DA = 8,000 ft, expect approximately 24% less power available than at sea level standard conditions. Always verify with the aircraft's POH hover performance charts.
Default assumptions & sources
Every default value the calculator starts with, the realistic range you'd see in the field, and the source we used to set it.
| Input | Default | Typical range | Source |
|---|---|---|---|
| Field elevation | 2,000 ft | -300 to 15,000 ft | Sectional chart, airport directory, or GPS |
| Altimeter setting | 29.92 in Hg | 28.0 to 31.0 in Hg | ATIS, ASOS, AWOS, or Flight Service |
| OAT | 85°F | -40 to 130°F | OAT gauge or weather observation |
| Hover loss rate | ~3%/1000 ft | varies by aircraft | Rule of thumb; verify with POH hover performance chart |
What's not modeled
The calculator covers the major cost and time line items. These additional factors apply in some cases but aren't included in the estimate:
- Humidity / dewpoint - the standard FAA density altitude formula does not account for humidity. Humid air is slightly less dense than dry air at the same temperature, so true density altitude on a humid day is slightly higher than calculated.
- Aircraft-specific performance curves - the 3%/1,000 ft hover loss is a rough rule of thumb only. Some helicopters perform better, some worse.
- Power available limits other than density - engine condition, contamination, mixture, oil temperature, and other factors all affect actual power available.
Frequently asked questions
What is density altitude?
Density altitude is the altitude at which the standard atmosphere has the same air density as your current conditions. It accounts for non-standard pressure (via pressure altitude) and non-standard temperature. Aircraft performance is driven by air density, so density altitude is the single most important performance reference.
#Why is density altitude critical for helicopters specifically?
Helicopters are power-limited at high density altitudes much more than fixed-wing aircraft. A helicopter that can hover IGE (in ground effect) at sea level may not be able to hover OGE (out of ground effect) at DA = 8,000 ft. NTSB accident reports include many cases of helicopters operating beyond their performance limits at high DA.
#How does the 3%-per-1000-ft hover loss rule work?
It is a rough heuristic: for every 1,000 ft of density altitude, expect approximately 3% less power available for hover. At DA = 5,000 ft, expect ~15% less power than sea level standard. The rule is approximate - actual numbers depend on engine type, rotor system, and external conditions. Verify with the aircraft POH hover performance chart.
#Where can I get a more accurate density altitude reading?
Many EFB apps (ForeFlight, Garmin Pilot) compute density altitude from current METAR data. Glass cockpits (G500H, GTN integration) often display DA directly. AWOS at many airports broadcasts density altitude when conditions warrant.
#Related guides & tools
This calculator provides estimates only. Actual aircraft performance and regulatory compliance vary by specific aircraft serial number, density altitude, gross weight, equipment installations, and operator's FAA-approved General Operations Manual / OpSpec. Always verify with primary sources: the FAA (faa.gov), 14 CFR (eCFR at ecfr.gov), your aircraft Rotorcraft Flight Manual (RFM) or Pilot Operating Handbook (POH), the relevant FAA Advisory Circular, and NTSB safety studies for the operational profile.