Introduction
Density altitude is the altitude at which the air around you actually "feels" like it behaves, based on its true thickness. Hot, humid, or low-pressure air is thinner than normal. Thin air means airplane wings produce less lift, engines make less power, and propellers are less efficient.1 This makes takeoff rolls longer and climb rates slower. Pilots, flight instructors, and dispatchers need to know the density altitude before every flight to stay safe.
This free density altitude calculator works in two clear stages. In Stage 1, you enter your field elevation and altimeter setting to find pressure altitude. In Stage 2, you add the outside air temperature and humidity to get the final density altitude. The tool also shows you air density, station pressure, ISA temperature deviation, and a full step-by-step solution so you can see exactly how each number was found. A built-in chart plots how density altitude changes as temperature rises or falls, giving you a quick visual reference for flight planning.
How to Use Our Density Altitude Calculator
Enter your airport conditions below to find the density altitude at your location. The calculator will return your density altitude in feet and meters, along with air density, station pressure, ISA deviation, and a full step-by-step solution.
Field / Station Elevation: Type the elevation of your airport or weather station above sea level. You can switch between feet and meters using the unit buttons.
Altimeter Setting: Enter the current altimeter setting shown in the Kollsman window of your altimeter. This is not raw station pressure. You can enter it in inHg or hPa.
Pressure Altitude: This field fills in automatically from the elevation and altimeter setting you entered above. You can type over it if you already know your pressure altitude. Click "Re-sync from Stage 1" to restore the auto value.
Outside Air Temperature (OAT): Enter the current air temperature at your location. You can choose between °F, °C, or Kelvin.
Moisture Input: Pick either Relative Humidity or Dew Point. If you choose Relative Humidity, enter a value from 0 to 100 percent. If you choose Dew Point, enter the dew point temperature. Set this to 0% humidity if you want a dry-air result that matches most AWOS reports.
Press the Calculate button to see your results. Press Reset / Clear All to start over with standard day values.
What Is Density Altitude?
Density altitude is how the air around you "feels" to an airplane. It tells you how thick or thin the air really is at your location. When the air is thin, wings produce less lift and engines make less power. This means your plane needs more runway to take off and climbs slower than normal.
Density altitude is not a true height above the ground. It is the altitude in the standard atmosphere where the air density matches what you have right now.1 For example, if you are sitting at a field that is 2,000 feet above sea level but the density altitude is 5,000 feet, your airplane will perform as if it were at 5,000 feet.
What Changes Density Altitude?
Three main things raise density altitude and make air thinner:
- High temperature: Hot air is less dense than cold air.1 On a hot summer day, density altitude can be thousands of feet higher than the actual field elevation.
- Low air pressure: When the barometric pressure drops, the air becomes thinner. Your altimeter setting directly reflects this.
- High humidity: Moist air is lighter than dry air, because water vapor is lighter than air.1 Humidity is usually a smaller effect than temperature and pressure, but it does contribute.1
Why Density Altitude Matters for Pilots
Every pilot needs to know the density altitude before flying. It affects takeoff distance, climb rate, engine power output, and true airspeed. For example, at a pressure altitude of 5,000 feet and 20 °C above standard, density altitude is above 7,000 feet and a takeoff ground run of 790 feet can grow to about 1,000 feet.1 Alongside density altitude, pilots should also evaluate crosswind components and estimated flight times as part of thorough preflight planning.
The results banner uses four rough bands: below 1,000 feet is near standard, 1,000 to 3,000 feet means slight performance loss, 3,000 to 6,000 feet means noticeably longer takeoff rolls, and above 6,000 feet means a large performance loss. The bands are only a guide. Your aircraft performance charts give the real numbers.
How This Calculator Works
This calculator uses a two-stage process. In Stage 1, it converts your field elevation and altimeter setting (the Kollsman window value) into pressure altitude. In Stage 2, it combines that pressure altitude with the outside air temperature and moisture level to find the true density altitude. It uses the virtual temperature, the temperature dry air would need to have the same pressure and density as the moist air, so humidity is included.3
The results also show you the actual station pressure, air density in both metric and imperial units, relative air density compared to sea level, and the ISA temperature deviation. A full step-by-step solution with formulas is provided so you can verify every number yourself.