Latitude and longitude to MGRS

Encodes a WGS 84 latitude and longitude as an grid reference at any precision, truncating (never rounding) as the standard requires.

Go the other way: MGRS to latitude and longitude →

Computing your own values needs JavaScript and WebAssembly. The worked example below was computed when this page was built, and the documentation under "How we got this" applies.

17TNE8630977770

The MGRS reference is 17T NE 86309 77770, a 1 m square.

MGRS (spaced)
Square size

Provenance

Computed by: geodesy.grid-ref.mgrs-forward 1.0.0, core 0.1.0
Model: NGA MGRS (AA lettering) over UTM and UPS on WGS 84
Accuracy: Exact; the reference names the square containing the point (truncation)
Notes: None
Cites: National Geospatial-Intelligence Agency, Military Grid Reference System, NGA.STND.0037; Karney, C. F. F., GeographicLib, GeographicLib MGRS and UTMUPS classes

Something look off?

How we got thisFormula, worked example, sources, and proof

Model: NGA MGRS (AA lettering) over UTM and UPS on WGS 84

Show your work

Grid position
the UTM or UPS zone, easting, and northing the point falls at
40.446111°, -79.982222° = zone 17, 586,310 m E, 4,477,770 m N
Square
how much of the easting and northing the chosen precision keeps
precision 5 = 1 m across
Reference
zone, band, 100 km square, then the kept digits
zone 17 at precision 5 = 17TNE8630977770

The same steps an agent gets from the MCP server with explain: true.

Accuracy: Exact; the reference names the square containing the point (truncation)

When to use this: Use this when a position has to be written the way military and emergency services read it: an MGRS reference at the precision you choose, from a 100 km square down to a meter. It is the form used on ground operations, in search and rescue, and on maps that carry the grid.

Limitations: The reference names the square that contains the point, because MGRS truncates rather than rounds: a ten-digit reference is a one-meter square whose south-west corner is the position given, and a shorter one names a larger square. It is defined on UTM and UPS, so it carries their zone structure, and the coordinates here are WGS 84.

Worked example: Pittsburgh at 1 m. Source: add-geodesy-suite scenario: 17TNE8630977770. It is golden test vector v001, and every build checks the tool still gives its answer within its tolerance.

You enter

Latitude: 40.446111 deg
Longitude: -79.982222 deg

You get

MGRS: 17TNE8630977770
MGRS (spaced): 17T NE 86309 77770
Square size: 1 m

Review: Not yet independently reviewed by a geodesist.

Last verified: 2026-09-18, when a maintainer last confirmed this tool's sources at the issuer. See the sources ledger.

Status: version 1.0.0, core 0.1.0. See this tool in the verification report.

Changes

2026-09-19, changed: MGRS encode and decode are now stable. They match the Washington Monument example in the FGDC US National Grid standard and 2,000 references from NGA GEOTRANS; where GEOTRANS's own projection is 1.5 cm off near the poles and in Svalbard, PROJ confirms geoprims. Results are unchanged. Changelog

Checked against: 25 golden test vectors (download the test vectors, each with its source and tolerance). See how results are checked and every source.

Sources

Military Grid Reference System, NGA.STND.0037, National Geospatial-Intelligence Agency, NGA.STND.0037_2.0.0_GRIDS. MGRS lettering (AA scheme) and truncation. Read free.
GeographicLib MGRS and UTMUPS classes, Karney, C. F. F., GeographicLib, GeographicLib 2.x. MGRS.cpp: band tolerance, square validation, UPS lettering. Read free.

Terms

MGRS: Military Grid Reference System: UTM and UPS coordinates written as a zone, a latitude band, a two-letter 100 km square, and digits, like 17T NE 86309 77770. Source: NGA.STND.0037 MGRS

MGRS — Military Grid Reference System

UTM and UPS coordinates written as a zone, a latitude band, a two-letter 100 km square, and digits, like 17T NE 86309 77770.

Source: NGA.STND.0037 MGRS

Learn the concept: MGRS and USNG coordinates explained, UTM coordinates explained

Your values