Wrong Altimeter Setting Error Calculator
Dial in the wrong altimeter setting and every altitude you fly is wrong by a fixed amount — compute exactly how much and in which direction.
The classic blunder: descending from flight levels and leaving 29.92 set while local pressure is 29.45 — you fly 470 ft lower than every altitude you think you're holding.
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.
Dial in the wrong altimeter setting and every altitude you fly is wrong by a fixed amount — compute exactly how much and in which direction.
About Wrong Altimeter Setting Error Calculator
Altimeter-setting blunders are embarrassingly simple and persistently lethal: one inch of mercury equals a thousand feet, in whichever direction you got it wrong. This calculator takes the setting you actually dialed, the correct local setting and your indicated altitude, and returns the signed error with its operational meaning — including the notorious forgot-to-leave-standard descent case where the entire approach is flown hundreds of feet low.
How to use Wrong Altimeter Setting Error 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 error(ft) ≈ (setting dialed − correct setting) × 1,000; actual ≈ indicated − error substituted step by step.
- 4Adjust inputs (or flip the unit toggle) until the scenario matches yours, then copy or share the result.
Why use Wrong Altimeter Setting Error Calculator?
- ✓Instant, free and private — every calculation runs in your browser, nothing is uploaded
- ✓Built on the published formula error(ft) ≈ (setting dialed − correct setting) × 1,000; actual ≈ indicated − error with sources cited on the page
- ✓The classic blunder: descending from flight levels and leaving 29.92 set while local pressure is 29.45 — you fly 470 ft lower than every altitude you think you're holding.
- ✓Switch units, tweak any input and watch every result update live
Frequently asked questions
Which direction does the error go?+
If the number in your Kollsman window is higher than the real local setting, your altimeter is over-reading: you are lower than indicated — the dangerous direction. Window lower than reality means you're higher than indicated. The mnemonic 'high to low, look out below' covers both pressure changes en route and dialing errors.
How does this differ from flying high-to-low without resetting?+
It's the same physics. Cruising from a 30.10 region into a 29.60 region without updating is mathematically identical to dialing 0.50 too high: you end up 500 ft lower than indicated. ATC's periodic altimeter broadcasts and the IFR requirement to set the nearest station's value exist to keep that drift trimmed.
What is the preflight altimeter accuracy check?+
With the correct local setting dialed, the altimeter on the ramp should read field elevation within ±75 ft for IFR flight (the common AIM 7-2-3 guidance figure). A bigger split means the instrument, not just the setting, is suspect — this tool's tolerance verdict uses the same 75 ft yardstick.
Does ADS-B or Mode C save me from my own setting error?+
Partly, for ATC: transponders report pressure altitude on the 29.92 datum regardless of your dialing, so the controller's display stays honest. But your terrain clearance, approach minimums and traffic-pattern altitude are flown off the cockpit altimeter — the one with the wrong number in it. The error is all yours.
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