Density Altitude Calculator

Calculator Input

Calculation Mode

Field Elevation (ft)

Altimeter Setting (inHg)

Pressure Altitude (ft)

Outside Air Temperature (°C)

Dew Point (°C)

Plotly Graph

The graph compares temperature with resulting density altitude while holding the entered pressure conditions constant.

Example Data Table

Scenario	Field Elevation (ft)	Altimeter (inHg)	OAT (°C)	Dew Point (°C)	Density Altitude (ft)
Cool sea level morning	0	30.10	10	6	-685
Warm regional airport	2,500	29.85	28	12	4,818
Hot mountain field	5,200	29.70	32	8	8,651
Humid summer afternoon	1,200	29.60	34	24	4,376

Formula Used

This calculator estimates station pressure, moist air density, and the equivalent standard atmosphere altitude for that density.

1) Station pressure from elevation and altimeter:
Pstation ≈ Altimeter × (1 − 6.87535×10^-6 × elevation_ft)^5.2559

2) Vapor pressure from dew point:
e = 6.112 × exp((17.67 × Td) / (Td + 243.5))

3) Moist air density:
ρ = (Pd / (Rd × T)) + (Pv / (Rv × T))

4) Density altitude from density ratio:
σ = ρ / ρ0
DA = (1 − σ^(1 / 4.2558797)) / 6.8755856×10^-6

5) Quick cockpit estimate:
DA ≈ Pressure Altitude + 120 × (OAT − ISA Temperature)

How to Use This Calculator

Select whether you want to calculate from field elevation and altimeter setting or from direct pressure altitude.
Enter the outside air temperature and dew point in degrees Celsius.
Submit the form to display the result beneath the header and above the input form.
Review density altitude, pressure altitude, ISA temperature, humidity influence, and air density.
Use the CSV or PDF buttons to export the current result.
Check the graph to see how density altitude changes as temperature changes.

About Density Altitude

Density altitude tells you how dense the air feels to an aircraft or moving object compared with the standard atmosphere. Higher values usually mean thinner air, which can reduce lift, propeller efficiency, and engine performance.

Temperature pushes density altitude upward quickly. Pressure also matters because lower pressure reduces air density even before temperature is considered. Moisture adds a smaller but real effect because water vapor is lighter than dry air.

For physics work, density altitude is a useful way to combine pressure, temperature, and humidity into one operational number. It helps you compare present air conditions against standard atmosphere assumptions used in many performance references.

FAQs

1) What is density altitude?

Density altitude is the altitude in the standard atmosphere that has the same air density as the current conditions. It combines pressure, temperature, and moisture into one performance-focused value.

2) Why is density altitude important?

High density altitude means thinner air. That usually lowers lift, propeller thrust, and engine output. It can increase takeoff distance and reduce climb performance.

3) How is pressure altitude different from density altitude?

Pressure altitude depends only on pressure conditions after standardizing sea level reference. Density altitude starts with pressure altitude, then adjusts for temperature and moisture effects.

4) Does humidity really matter?

Yes. Humidity usually has a smaller effect than temperature, but moist air is less dense than dry air. On hot days, the added increase can still matter.

5) Why does the calculator ask for dew point?

Dew point helps estimate the vapor pressure in the air. That lets the calculator include moisture in the air density equation instead of using only dry air assumptions.

6) What does ISA temperature mean?

ISA temperature is the standard atmosphere temperature expected at a given pressure altitude. Comparing actual temperature to ISA shows how far current conditions depart from standard.

7) Is the quick estimate exact?

No. The quick estimate is a common cockpit shortcut. It is useful for rough checks, but the moist air density method is more complete.

8) Can density altitude be lower than field elevation?

Yes. Cold, high-pressure air can make density altitude lower than the airport elevation. That means the air is denser than standard for that location.