Density Altitude vs True Altitude Explainer Calculator
One set of inputs, four altitudes out — indicated, pressure, density and approximate true altitude — so the alphabet soup finally makes sense.
“High to low or hot to cold — look out below.” In colder-than-ISA air the altimeter overstates your height; the error grows with height above the station whose QNH you are using.
Formula
⚠️ For flight planning and education only — always verify against your aircraft's POH/AFM, official weather sources and certified instruments. Not for primary navigation or airworthiness decisions.
One set of inputs, four altitudes out — indicated, pressure, density and approximate true altitude — so the alphabet soup finally makes sense.
About Density Altitude vs True Altitude Explainer Calculator
Student pilots juggle five named altitudes, and most explanations stay theoretical. This calculator makes them concrete: enter what your altimeter shows, the QNH, the outside temperature and the reporting station's elevation, and it returns pressure altitude, density altitude and an approximate true altitude with the ICAO temperature-error formula — flagging the dangerous cold-day case where every one of those numbers sits below what the needle claims.
How to use Density Altitude vs True Altitude Explainer Calculator
- 1Enter — sensible defaults are pre-filled so you see a worked result immediately.
- 2Read the live results: .
- 3Check the "With your numbers" line to see the formula PA = IA + (29.92 − QNH)×1000; DA = PA + 118.8×(OAT − ISA); ΔH_temp ≈ H_above-stn × ISA-dev / T substituted step by step.
- 4Adjust inputs (or flip the unit toggle) until the scenario matches yours, then copy or share the result.
Why use Density Altitude vs True Altitude Explainer Calculator?
- ✓Instant, free and private — every calculation runs in your browser, nothing is uploaded
- ✓Built on the published formula PA = IA + (29.92 − QNH)×1000; DA = PA + 118.8×(OAT − ISA); ΔH_temp ≈ H_above-stn × ISA-dev / T with sources cited on the page
- ✓“High to low or hot to cold — look out below.” In colder-than-ISA air the altimeter overstates your height; the error grows with height above the station whose QNH you are using.
- ✓Switch units, tweak any input and watch every result update live
Frequently asked questions
What is the difference between the five altitudes?+
Indicated is what the altimeter reads. Pressure altitude is indicated with 29.92 set — the standard-datum height. Density altitude is pressure altitude corrected for temperature — a performance number, not a height. True altitude is your real height above sea level. Absolute altitude (not computed here) is height above the terrain directly below.
Why does cold air make my altimeter lie high?+
The altimeter assumes the ISA pressure-height relationship. Cold air is denser and its pressure falls faster with height, so a given pressure level sits physically lower than ISA predicts. Flying a constant indicated altitude in cold air therefore means flying a lower true altitude — the reason cold-temperature corrections exist for approaches near terrain.
When must I legally apply cold-temperature corrections?+
Many states publish cold-temperature-restricted airports (the FAA lists them in the Notices and CTA procedures) where corrections to approach segment altitudes are mandatory below a trigger temperature. Even where not mandatory, PANS-OPS and the AIM recommend correcting minimum altitudes whenever temperature is well below ISA and terrain matters.
How accurate is the true-altitude estimate here?+
It uses the ICAO linearized correction — height above station × ISA deviation / absolute temperature — which is the same first-order formula behind published correction tables. It is excellent for typical GA heights above the station (±2,000–8,000 ft) and degrades for extreme deviations; published tables and your avionics' corrections take precedence for instrument procedures.
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