True ↔ Magnetic Heading Converter
Apply variation in either direction with the sign handled for you — east is least, west is best, and the mistake is never yours again.
Variation is the angle between true and magnetic north at your location — printed as isogonic lines on every sectional. It ranges from 0° (the agonic line through the US Midwest) past 20° in the Pacific Northwest and polar regions.
Formula
⚠️ For flight planning and education only — verify with official sources and certified equipment. Not for primary navigation.
Apply variation in either direction with the sign handled for you — east is least, west is best, and the mistake is never yours again.
About True ↔ Magnetic Heading Converter
Charts and winds speak true; compasses and runways speak magnetic; the translation — variation — flips sign depending on direction and hemisphere of conversion, which is exactly where checkride answers and real headings go wrong. This converter applies the rhyme ('east is least, west is best') mechanically in either direction, displays which rule it used, and handles the wraparound, so the only judgment left is reading the isogonic line off the chart.
How to use True ↔ Magnetic Heading Converter
- 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 MAG = TRUE − east var (+ west var); TRUE = MAG + east var (− west var) substituted step by step.
- 4Adjust inputs (or flip the unit toggle) until the scenario matches yours, then copy or share the result.
Why use True ↔ Magnetic Heading Converter?
- ✓Instant, free and private — every calculation runs in your browser, nothing is uploaded
- ✓Built on the published formula MAG = TRUE − east var (+ west var); TRUE = MAG + east var (− west var) with sources cited on the page
- ✓Variation is the angle between true and magnetic north at your location — printed as isogonic lines on every sectional. It ranges from 0° (the agonic line through the US Midwest) past 20° in the Pacific Northwest and polar regions.
- ✓Switch units, tweak any input and watch every result update live
Frequently asked questions
Why do true and magnetic north differ at all?+
Earth's magnetic field is generated by a churning molten core, not its rotation axis: the magnetic pole sits in the Canadian Arctic (and wanders kilometres yearly). The angular difference at your longitude-latitude is the variation (navigators) or declination (geophysicists) — same angle, two professions.
Which direction does 'east is least' apply?+
Converting TRUE to MAGNETIC: subtract east variation, add west. Going the other way reverses the sign — the rhyme's silent failure mode. This tool's 'rule applied' line states the operation in full each time precisely so the reversed case never gets the un-reversed rhyme.
Does variation change over time?+
Yes — secular drift of several arcminutes to a tenth of a degree per year in places, which is why sectional isogonics carry dates, runway numbers get repainted (Oakland's 27s became 28s), and the World Magnetic Model is reissued every five years. For flight planning, the current chart's value is always the answer.
Where does deviation fit into this chain?+
After variation: deviation is your individual aircraft's compass error from onboard magnetism, listed on the compass correction card placard. The full chain — True ± Variation = Magnetic ± Deviation = Compass — is the TVMDC sequence our dedicated TVMDC trainer drills. This tool handles the V; the card handles the D.
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