Free utility · pilot rule-of-thumb

Density Altitude

Pressure altitude, density altitude, ISA spread, and a rough takeoff-penalty estimate. Same formulas every CFI teaches — wrapped in something you can pull up on your phone before pushing the throttle.

Inputs

Field elevation (ft MSL)

From the chart supplement or airport diagram.

Altimeter setting (inHg)

From METAR or ATIS. 29.92 = ISA standard.

Outside air temperature (OAT)

Dewpoint (optional — humidity advisory)

Only used for the high-humidity flag.

Verdict

—

Enter field elevation, altimeter, and OAT to compute density altitude.

DA risk bands

< 5,000 ftNormal — POH numbers apply

5,000–8,000High — plan longer takeoff, weaker climb

≥ 8,000 ftMountain — run POH charts at exact DA

Pressure altitude—

Density altitude—

ISA temp at PA—

ISA spread—

Est. takeoff penalty—

Rough rule: +1% per 100 ft DA above field elevation. Use POH for real numbers.

About this calculator

Uses the pilot rule-of-thumb formulas — pressure altitude via the altimeter offset from 29.92 inHg, density altitude via 120 ft per °C above ISA at that PA. Good to within a few hundred feet of the full atmospheric model. Not a replacement for your POH performance charts.

For a full pre-flight check including pilot currency + aircraft squawks + inspection countdowns, see AutoBrief.

AutoBrief

AutoBrief checks density altitude before every flight — and flags it in the morning brief if it crosses your school's threshold.

AI pre-flight GO/NO-GO for flight schools.

See AutoBrief →