What format should the MGRS string be in?

Use the grid zone designator, the two-letter 100 km square, then equal-length easting and northing digits, for example 30U XC 99319 10158. Spaces are optional; this tool accepts the string with or without them.

How is precision recovered from the digits?

The easting and northing digit groups must be the same length. Five digits each means 1 metre precision; fewer digits mean coarser precision, and the value is scaled to the centre of the implied cell.

Why are the I and O letters never present?

MGRS skips I and O throughout because they look like the digits 1 and 0. A valid MGRS string will never contain them, and this tool rejects them.

What datum does the result use?

The output is WGS-84 decimal latitude and longitude, the datum used by GPS and most modern maps, computed on the WGS-84 ellipsoid.

MGRS to Lat/Lng Converter

This tool decodes a Military Grid Reference System (MGRS) string back into WGS-84 decimal latitude and longitude. It is the inverse of the lat/long to MGRS encoder and is handy when a map, radio report or dataset gives you a grid reference you need as GPS coordinates.

How it works

The string is split into three parts — the grid zone designator, the 100 km square letters and the numeric digits:

30U XC 99319 10158
└┬┘ └┬┘ └──┬──┘ └──┬──┘
 GZD  sq   easting  northing

The square letters are mapped back to their 100 km easting and northing offsets within the zone, using the same column/row alphabets the encoder uses (with I and O skipped). The numeric digits are scaled to metres and added on, giving a full UTM easting and northing. An inverse transverse Mercator projection on the WGS-84 ellipsoid then recovers the latitude and longitude.

Tips and notes

The easting and northing digit groups must have equal length; this tool centres the position within the implied cell so coarse references still land sensibly. MGRS is valid only between about 80°S and 84°N. Everything runs locally in your browser. To encode coordinates into MGRS, use the Lat/Lng to MGRS converter.