MGRS ↔ Lat/Long Converter

Field guide: MGRS ↔ Lat/Long Converter

The Military Grid Reference System is how NATO forces, search-and-rescue teams and an increasing number of preparedness-minded civilians describe positions: a reference like 43R FM 12345 67890 names a 1-metre square on Earth using a grid zone, a 100 km square pair of letters, and easting/northing digits. Its genius is graduated precision — drop digits and the same reference naturally describes a 10 m, 100 m, 1 km or 10 km square, which is why radio protocols love it. This converter translates both directions against WGS84, using the standard NGA lettering scheme (the same tables as GEOTRANS), and shows the underlying UTM coordinates for cross-checking.

The math underneath is the UTM transverse-Mercator projection (Snyder's series, sub-metre accurate) plus the MGRS lettering rules: column letters cycling A–Z minus I and O across three zone-dependent sets, row letters cycling every 2,000 km with the even-zone offset, and latitude bands C through X. Edge cases the cheap converters miss — the Norway 32V widening and the four Svalbard zones — are handled. Conversion runs in your browser; positions are never transmitted, which matters for the use cases MGRS tends to serve.

Field tips

• Reading an MGRS reference aloud: digits split evenly — in 43R FM 12345 67890, easting is 12345, northing is 67890. An odd total digit count is always a transcription error.
• Going MGRS → lat/long returns the square's southwest corner per convention. For a 1 km square's centre, add 500 to both easting and northing digits first.
• Position formats are not datums: MGRS here is WGS84. References derived from old maps on local datums (e.g., Everest/Indian) can be hundreds of metres off — check the map legend.

Conversion math follows the cited NGA/USGS standards and is unit-tested against published vectors. For navigation, never rely on a single tool or device — cross-check positions and carry a map and compass.