Pressure Altitude from Station Pressure
Convert a raw station/absolute pressure reading (hPa or inHg) directly into pressure altitude with the exact ISA barometric inversion — no QNH needed.
This is the exact ISA inversion (no linear rule-of-thumb): 850 hPa — a favorite meteorology level — corresponds to about 4,780 ft pressure altitude. It is the same formula inside altimeters and drone baro sensors.
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.
Convert a raw station/absolute pressure reading (hPa or inHg) directly into pressure altitude with the exact ISA barometric inversion — no QNH needed.
About Pressure Altitude from Station Pressure
Sometimes you don't have a QNH — you have a raw pressure number: a hiking barometer, a drone's baro sensor log, a home weather station, or a meteorology chart's 850 hPa surface. This converter applies the exact ISA pressure-height inversion (the real formula, not the 27-ft linearization) to turn absolute pressure straight into pressure altitude, and shows the pressure ratio δ for engineers who want the dimensionless form.
How to use Pressure Altitude from Station Pressure
- 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(ft) = 145,366.45 × (1 − (p/1013.25)^0.190284) substituted step by step.
- 4Adjust inputs (or flip the unit toggle) until the scenario matches yours, then copy or share the result.
Why use Pressure Altitude from Station Pressure?
- ✓Instant, free and private — every calculation runs in your browser, nothing is uploaded
- ✓Built on the published formula PA(ft) = 145,366.45 × (1 − (p/1013.25)^0.190284) with sources cited on the page
- ✓This is the exact ISA inversion (no linear rule-of-thumb): 850 hPa — a favorite meteorology level — corresponds to about 4,780 ft pressure altitude. It is the same formula inside altimeters and drone baro sensors.
- ✓Switch units, tweak any input and watch every result update live
Frequently asked questions
How is station pressure different from the altimeter setting?+
Station pressure is what a barometer at the site actually measures. The altimeter setting (QNH) is that measurement artificially reduced to sea level so altimeters read field elevation on the ground. If you feed this tool a QNH you'll get roughly zero altitude — feed it the raw, unreduced reading instead.
Why does my drone log pressure instead of altitude?+
Baro chips (BMP/MS56xx-class) sense pressure; altitude is derived in firmware with exactly this ISA formula. Logging the raw pascals preserves the measurement so altitude can be recomputed against a better reference later — paste any logged value here (in hPa) to decode what the sensor saw.
What are the standard meteorological pressure levels in altitude terms?+
Roughly: 1000 hPa ≈ 360 ft, 925 hPa ≈ 2,500 ft, 850 hPa ≈ 4,780 ft, 700 hPa ≈ 9,880 ft, 500 hPa ≈ 18,290 ft, 300 hPa ≈ 30,070 ft. Forecast discussions of '500 mb troughs' are talking about the FL180 neighborhood — run any level through this tool for the exact figure.
Is the formula valid at any altitude?+
The exponent 0.190284 and constant 145,366.45 ft encode the ISA troposphere (sea level to 11 km / 36,089 ft), where temperature lapses linearly. Above the tropopause the atmosphere turns isothermal and a different (exponential) relation applies, so treat results above ~36,000 ft as out of scope.
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