E6B Calc How to calculate density altitude from pressure altitude and temperature
First turn field elevation and altimeter setting into pressure altitude. Then correct that for how far the temperature sits from standard. At a 5,000 ft field with 29.92 inHg and 30 °C on the ramp: pressure altitude comes out at 5,000 ft, density altitude at 7,800 ft — enough to change how the takeoff roll feels. E6B Calc does both steps on its free Density Altitude screen.
Why density altitude matters before takeoff
Engines, propellers and wings care about air density, not the number on the altimeter. Thin air at a hot, high field means a longer takeoff roll, a weaker climb and a quieter-feeling engine.
Your POH charts already take pressure altitude and temperature as inputs, so technically you could skip this number entirely and go straight to the chart. Most pilots still find it worth having, because one figure that says "the day is costing you 2,800 ft" sticks in a way two chart lookups don't.
Step 1: how to calculate pressure altitude with the altimeter setting
Pressure altitude is the height in the standard atmosphere that matches today's pressure: elevation plus roughly 1,000 ft for every inch of mercury below 29.92, or about 30 ft per hPa below 1013. That's the shortcut. The app skips the shortcut and runs the full standard-atmosphere equation.
Step 2: from pressure altitude and temperature to density altitude
Standard temperature is 15 °C at sea level, falling about 2 °C per 1,000 ft. The classroom rule adds 120 ft of density altitude per degree above standard — fine for a gut check, not for reading a chart that's already close to the edge. In the worked example below, the rule lands near 8,000 ft; the ICAO equations the app actually runs give 7,800 ft. 200 ft doesn't sound like much until it's the margin at the end of the runway.
How to calculate density altitude in E6B Calc
- On the E6B screen, open Density Altitude under Flight.
- Type the Field elevation in feet. Leave it empty for sea level.
- Enter the Altimeter setting. It starts at standard pressure; the unit (inHg or hPa) follows Settings > Units of measurement.
- Enter the Outside air temperature. Use the plus/minus key for a negative value.
- Read Pressure altitude, Density altitude and ISA deviation under the inputs. Altitudes are rounded to the nearest 10 ft.
Worked examples
| Field elevation | Altimeter setting | Outside air temperature | Pressure altitude | Density altitude | ISA deviation |
|---|---|---|---|---|---|
| 5,000 ft | 29.92 inHg | 30 °C | 5,000 ft | 7,800 ft | +24.9 °C |
| 2,000 ft | 1008 hPa | 30 °C | 2,140 ft | 4,340 ft | +19.2 °C |
| 5,434 ft | 30.12 inHg | 30.6 °C | 5,250 ft | 8,170 ft | +26.0 °C |
Row two: the low pressure (1008 hPa) alone adds 140 ft before temperature even gets counted. Row three: a high altimeter setting pulls pressure altitude below field elevation, and the heat still shoves density altitude almost 2,750 ft above the field — the two effects don't cancel the way people expect. Switch temperature to °F and ISA deviation follows: 86 °F in the first row shows as +44.8 °F.
Is there a density altitude calculator with humidity?
No, though that would help on humid mornings. Humid air is a little lighter than dry, so a muggy day is a touch worse than the dry-air number suggests. E6B Calc computes dry air only, same as most flight computers and POH charts do. Pad your margin on a hot, humid morning instead.
Other ways to get density altitude in the app
- From a report: paste a METAR into the METAR & TAF Decoder, tap Use this report, add your field elevation, and it gives pressure and density altitude from the report's own altimeter and temperature.
- On the watch: the Apple Watch app has a Density Altitude screen with Digital Crown inputs.
- On the Home Screen: the Density Altitude widget (E6B Pro) shows your Home Field observation that you typed and saved.
Common mistakes
- Using indicated altitude on the ground instead of field elevation, or forgetting to set the current altimeter setting.
- Entering the dew point instead of the temperature.
- Mixing units: 1008 typed while the app is set to inHg is not a valid setting. Check the unit next to the field.
- Reading takeoff distance from density altitude alone when your POH chart asks for pressure altitude and temperature. Use what the chart asks for.
Questions and answers
What is the difference between pressure altitude and density altitude?
What is the density altitude formula?
Can I enter the altimeter setting in hPa?
How is this different from the density altitude window on an E6B?
You might also like
More E6B Calc guides
- How to calculate crosswind and headwind components, including the gust
- How to calculate wind correction angle, true heading and ground speed
- How to calculate true airspeed from calibrated airspeed (and Mach)
- How to calculate an aircraft's center of gravity: weight and balance step by step
- How to read a METAR and TAF report, group by group
- Aviation fuel calculation: endurance, fuel required, reserve and point of no return
- How to determine a holding pattern entry: direct, teardrop or parallel
- How far can you glide after an engine failure?
- How do you calculate the great-circle distance between two coordinates?
- How do you calculate climb gradient as a percentage?
- How do you calculate cloud base and freezing level?
- How do you put a Zulu time widget on your iPhone?
- Zulu Time Does Not Change for Daylight Saving
- All questions about E6B Calc
- Back to E6B Calc