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.

What is the MGRS to Lat/Lng Converter?

Convert a Military Grid Reference System (MGRS) string back to WGS-84 decimal latitude and longitude. Paste a grid reference such as 30U XC 99319 10158 and get precise geographic coordinates via the decoded UTM position and inverse projection. It runs free in your browser on Gera Tools, with nothing uploaded.

MGRS to Lat/Lng Converter

Name: MGRS to Lat/Lng Converter
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

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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.

MGRS precision levels explained

The digit pairs in an MGRS reference encode location precision. Equal-length easting and northing groups determine how precisely the position is specified:

Digit pairs	Precision	Typical use
1+1 (e.g. `3 1`)	10 km	Approximate area
2+2 (e.g. `99 10`)	1 km	Grid square
3+3 (e.g. `993 101`)	100 m	Standard military grid
4+4 (e.g. `9931 1015`)	10 m	Survey-grade field use
5+5 (e.g. `99319 10158`)	1 m	Precision targeting, engineering

When fewer than 5-digit pairs are given, the tool centres the recovered coordinates in the implied cell, which is the correct military interpretation.

What the output tells you

After decoding, the tool returns:

Decimal latitude — positive is north of the equator, negative is south.
Decimal longitude — positive is east of the prime meridian, negative is west.
UTM intermediate values — easting, northing and zone, visible so you can cross-check manually or feed them into another GIS tool.

For example, decoding 30U XC 99319 10158 returns a position in southern England, near the WGS-84 decimal coordinates of approximately 51.5°N, 0.0°E (near London). Paste those into any mapping application to verify.

Common errors when entering MGRS

Unequal digit groups: 30U XC 9931 10158 has 4 easting digits but 5 northing digits — this is invalid. Both must match.
Including I or O: These letters are never used in MGRS 100 km square identifiers because they resemble 1 and 0. If your source data contains them, it is likely a transcription error.
Missing grid zone: An entry of just XC 99319 10158 without the zone designator (the 30U part) cannot be decoded. MGRS always requires all three components.

Tips and notes

MGRS is valid only between about 80°S and 84°N — polar regions use the separate UPS grid. Everything runs locally in your browser. To encode coordinates into MGRS, use the Lat/Lng to MGRS converter.