https://www.coordinately.org/tools/mgrs-converter
MGRS Converter — Lat/Lon ↔ Military Grid Reference System | Coordinately · Coordinately
Convert between MGRS and latitude/longitude. Direction auto-detected; the result includes the 100-km grid square, precision level, equivalent UTM, and EPSG...
grid reference systemlat lonmgrsconvertermilitary
https://en.wikipedia.org/wiki/Military_grid_reference_system
Military Grid Reference System - Wikipedia
grid reference systemmilitarywikipedia