Density Altitude Calculator
Density altitude is pressure altitude corrected for non-standard temperature: at a 5,000 ft airport on a 30 °C day it is about 8,000 ft, so the aircraft performs as if it were 3,000 ft higher.
For general informational use. Verify critical aviation calculations and weather with an authoritative source.
Density altitude at a glance
The table shows density altitude for common field elevations and temperatures, with the altimeter at standard (29.92 inHg / 1013 hPa). Read across to see how fast a hot afternoon changes things: at a 4,000 ft airfield, going from 10 °C to 40 °C adds more than 3,500 ft.
| Field elevation | 10 °C | 20 °C | 30 °C | 40 °C |
|---|---|---|---|---|
| Sea level | −590 ft | 590 ft | 1,780 ft | 2,970 ft |
| 2,000 ft | 1,880 ft | 3,060 ft | 4,250 ft | 5,440 ft |
| 4,000 ft | 4,350 ft | 5,530 ft | 6,720 ft | 7,910 ft |
| 6,000 ft | 6,820 ft | 8,010 ft | 9,190 ft | 10,380 ft |
| 8,000 ft | 9,290 ft | 10,480 ft | 11,660 ft | 12,850 ft |
A low altimeter setting raises the result further: every 0.1 inHg below 29.92 adds about 100 ft of pressure altitude, and so about 100 ft of density altitude.
What a high density altitude does to a light aircraft
- Take-off roll: longer, because the engine makes less power, the propeller less thrust and the wing needs a higher true airspeed to lift off.
- Climb: weaker. Obstacle clearance after take-off is often the real limit, not runway length.
- Landing: the same indicated approach speed is a higher true airspeed and groundspeed, so the landing roll is longer too.
- Normally aspirated engines also need the mixture leaned for best power on the ground at high-elevation airfields, following the flight manual.
Scenario: summer afternoon in the mountains
An airfield at 6,000 ft reports 30 °C and an altimeter of 30.02 inHg. Pressure altitude is 6,000 − 100 = 5,900 ft. ISA there is about 3.3 °C, so the air is about 26.7 °C warmer than standard, giving a density altitude of roughly 9,070 ft. Many light singles have only a few hundred feet per minute of climb left at that density altitude. Plan an early-morning departure, reduce weight, and use the take-off distance chart in your flight manual with pressure altitude and temperature.
Common mistakes
- Entering the temperature in °F while the unit is set to °C.
- Using density altitude in the flight manual charts: most charts are entered with pressure altitude and actual temperature.
- Forgetting that density altitude changes through the day. Check it again for a midday return flight.
What density altitude tells you
Density altitude is the altitude in the standard atmosphere at which the air would have the same density as the air around you now. Hot, high and low-pressure days raise it. A higher density altitude means the wings, propeller and engine all perform as if the aircraft were higher than it really is: longer take-off rolls, weaker climbs and higher true airspeeds for the same indicated airspeed.
How to use it
- Enter the airport elevation in feet.
- Enter the current altimeter setting from the METAR or ATIS and choose inHg or hPa.
- Enter the outside air temperature and choose °C or °F.
- Read pressure altitude, the ISA temperature at that altitude, the deviation and the density altitude.
Method and calculation
Pressure altitude = field elevation + (29.92 − altimeter in inHg) × 1,000 ft. An altimeter in hPa is first converted to inHg (1 inHg = 33.8639 hPa). ISA temperature at the pressure altitude = 15 °C − 1.98 °C per 1,000 ft. Density altitude ≈ pressure altitude + 118.8 ft × (OAT − ISA temperature in °C). This is the widely taught approximation and is normally within about 1–2% of the exact value for light-aircraft planning.
Worked example and practical notes
Denver area example: field elevation 5,000 ft, altimeter 29.92 inHg, temperature 30 °C. Pressure altitude = 5,000 ft. ISA at 5,000 ft = 15 − 9.9 = 5.1 °C, so the air is 24.9 °C warmer than standard. Density altitude ≈ 5,000 + 118.8 × 24.9 ≈ 7,958 ft. The aircraft will perform roughly as if it were departing from almost 8,000 ft.
Quick reference
| Pressure altitude | Elevation + (29.92 − altimeter) × 1,000 ft |
|---|---|
| ISA temperature | 15 °C − 1.98 °C per 1,000 ft |
| Density altitude | PA + 118.8 × (OAT − ISA) |
Accuracy and practical tips
Humidity is not included. Moist air is slightly less dense, so on humid days the real density altitude is a little higher than this result. Always use the performance charts in your aircraft flight manual: they are built from pressure altitude and temperature, not from density altitude alone.
Method based on the standard atmosphere and FAA Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25) rules of thumb. Use your aircraft flight manual (AFM/POH) and approved flight-planning tools for real operations.
Last reviewed: October 2026
Read the guide: Density Altitude Explained: Hot and High Days
Frequently asked questions
Why does density altitude matter?
Engines make less power, propellers produce less thrust and wings produce less lift in thin air, so take-off and climb performance get worse as density altitude rises.
Is density altitude the same as pressure altitude?
Only when the temperature is exactly standard (ISA). On a hot day density altitude is higher than pressure altitude; on a cold day it is lower.
Does this include humidity?
No. The calculator uses the standard dry-air approximation. High humidity raises density altitude slightly further.
Can I use this instead of my POH charts?
No. Use it to understand conditions, then take performance figures from the aircraft flight manual using pressure altitude and temperature.