Have a GPS coordinate in latitude and longitude and want to use it in the field as MGRS? Then you go the other way: from WGS84 decimal degrees to an MGRS reference.
From lat/long to MGRS in steps
- Determine the UTM zone. The zone number (1–60) follows from the longitude, and the latitude band letter from the latitude. Together they form the grid zone, for example
31U. - Latitude/longitude → UTM. Using the UTM projection formulas you calculate the easting and northing in meters within that zone.
- UTM → MGRS. From the easting/northing you derive the 100 km square (two letters) and truncate the meters to the desired number of digits.
That way 52.3676, 4.9041 becomes an MGRS reference you can write down and pass along compactly.
Choose the right precision
Decide in advance how precise you need to be. For a rough designation a 4- or 6-digit code is enough (1 km and 100 m respectively); for an exact point use 10 digits (1 m). Carrying more digits than needed makes the code unnecessarily long.
Why use software
As with the reverse conversion, the formulas are laborious and error-prone to do by hand. On top of that, you have to watch out at zone boundaries. An app takes all of that off your hands.
Straight into MilMap
In MilMap you tap a point (or use your own GPS position) and you instantly see the MGRS coordinate appear. That way you turn a shared lat/long location into MGRS in a single action for field use — including the correct 100 km square and the desired precision.