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SESK: Stuff Everyone Should Know · sesk.info/sport-altimeter-inch-hg

A 1 inch change in the altimeter setting changes the indicated altitude by about how much?

About 1,000 feet per inch of mercury.

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  1. 100 feet
  2. 1,000 feet ✔
  3. 10,000 feet

Why: Pressure drops about one inch of mercury for every 1,000 feet you climb. So a wrong altimeter setting of 0.10 inch puts your altitude off by about 100 feet.

Huh, didn't know that: The barometric pressure window on an altimeter is sometimes called the Kollsman window.

The dad joke
Why did the altimeter get nervous? It was under a lot of pressure.
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References

Answer: 1,000 feet. Pressure drops about one inch of mercury for every 1,000 feet you climb. So a wrong altimeter setting of 0.10 inch puts your altitude off by about 100 feet.

  1. FAA Pilot's Handbook of Aeronautical Knowledge, Chapter 8 www.faa.gov/sites/faa.gov/files/10_phak_ch8.pdf
    1 inch of pressure is equal to approximately 1,000 feet of altitude
    Checked 2026-10-11.
  2. FAA Pilot's Handbook of Aeronautical Knowledge, Chapter 8 www.faa.gov/sites/faa.gov/files/10_phak_ch8.pdf
    the Kollsman window
    Checked 2026-10-11.

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