Density Alt Calculator
Density alt calculator works out Pressure altitude and Density altitude from Field elevation or altitude, Altitude unit and Altimeter setting (QNH). The default figures on this page give density altitude of 1.2 ft; change any entry and the result, the working and the sources update together.
Your figures
Updates as you typeHow this is worked out
3 steps
- An altimeter setting of 29.92 inHg corresponds to an ISA offset of 1.2 ft.
- Pressure altitude = 0 ft field elevation + 1.2 ft = 1.2 ft (the 1000 ft per inHg rule of thumb gives 0 ft).
- At that pressure altitude p = 101320.76 Pa; with the temperature taken as standard (15 C) the density is 1.224937 kg/m3, i.e. a density altitude of 1.2 ft.
Its 5 worked examples are re-run on every release, last on 15 September 2026. What changed
Sources and references
4 sources
What the density alt calculator calculates
Works the ICAO Standard Atmosphere and the basic aerodynamic relations: pressure altitude, density altitude, pressure, temperature and density at altitude, true airspeed, Mach number, dynamic pressure, lift and drag, wing loading and stall speed.
How to use this density alt calculator
Enter Field elevation or altitude, Altitude unit, Altimeter setting (QNH) and Pressure unit. Pressure altitude updates as you type. Change one figure at a time to see what drives the result.
How the result is worked out
Open “How this is worked out” beside the result for the step-by-step calculation behind Pressure altitude, Density altitude and Static pressure.
The method follows ICAO Doc 7488, Manual of the ICAO Standard Atmosphere (extended to 80 km), U.S. Standard Atmosphere, 1976 (NASA-TM-X-74335), NASA Glenn Research Center, Beginner’s Guide to Aeronautics: lift and drag equations, dynamic pressure, speed of sound and FAA Pilot’s Handbook of Aeronautical Knowledge (FAA-H-8083-25C), Chapter 4.
What you can compare
Change one input at a time to see how it affects Pressure altitude, Density altitude and Static pressure. The inputs you can vary are Field elevation or altitude, Altitude unit, Altimeter setting (QNH), Pressure unit, Outside air temperature and Temperature unit.
Understanding Pressure altitude, Density altitude and Static pressure
For planning and study. Aircraft performance must be taken from the approved flight manual for the specific aircraft; the standard atmosphere describes a reference day, not the one you are flying in.
Results are general information, not financial, tax, legal, medical or engineering advice. Check any decision that matters with a qualified professional.
See something wrong? Report a problem with this calculator
Frequently asked questions
How to calculate density alt?
Works the ICAO Standard Atmosphere and the basic aerodynamic relations: pressure altitude, density altitude, pressure, temperature and density at altitude, true airspeed, Mach number, dynamic pressure, lift and drag. Open “How this is worked out” beside the result to see each step for your own figures.
How to use density alt chart?
It needs Field elevation or altitude, Altitude unit, Altimeter setting (QNH), Pressure unit, Outside air temperature and Temperature unit. Nothing else is required, and the figures stay in your browser.
How can I calculate density?
The result gives Pressure altitude, Density altitude, Static pressure, Temperature used, Air density and Density ratio to sea level, each labelled with its unit so the figure can be read on its own.
Why is density alt important?
Works the ICAO Standard Atmosphere and the basic aerodynamic relations: pressure altitude, density altitude, pressure, temperature and density at altitude, true airspeed, Mach number, dynamic pressure, lift and drag. On the figures this page opens with — field elevation or altitude 5,000 — the density altitude is 1.2 ft. Put your own figures in their place and the working updates beside the result.
What information do I need for the density alt calculator?
You need Field elevation or altitude, Altitude unit, Altimeter setting (QNH), Pressure unit, Outside air temperature, Temperature unit, Airspeed (calibrated, or true for Mach) and Speed unit. The page opens with default figures that give density altitude of 1.2 ft, so you can see the scale before entering your own.
What does this density alt calculator show?
It shows Pressure altitude, Density altitude, Static pressure, Temperature used, Air density, Density ratio to sea level, Speed of sound and True airspeed, with the working and any warnings for your entries.