The Military Grid Reference System (MGRS) is how NATO forces, search and rescue teams and many fire services give a position: a grid zone such as 18T, a two-letter 100 km square such as WL, and an even number of digits for the easting and northing inside that square. The US National Grid (USNG), used by FEMA and US emergency services, writes exactly the same references, so this converter handles both. Paste a reference with or without spaces and the map jumps to it and draws the square it stands for, because an MGRS reference is not a point but a square: "18T WL 80 04" is a 1 km square, "18T WL 80735 04695" a 1 m square. The panel gives the centre in decimal degrees and degrees-minutes-seconds and the UTM coordinates of the corner. In the other direction, click the map, search for a town or press "Use my location" and read the reference at the precision you choose, ready to copy with or without spaces. The grid on the map shows the zone and band boundaries and, as you zoom in, the lettered 100 km squares and the 10 km, 1 km and 100 m lines, so you can read references off the map as you would on a paper map sheet. A whole list of references or coordinates can be converted at once and downloaded as CSV.
How to use it
- Type or paste an MGRS or USNG reference (spaces are optional) and press "Show", or click the map, search a town or press "Use my location".
- Read the centre of the square in latitude and longitude, or the reference of your point, and copy it.
- Choose the precision from 1 m (10 digits) to 100 km, and zoom in to see the 100 km squares and the finer grid lines.
- For many points, open "Convert a list", paste one reference or coordinate pair per line and download the CSV.
How accurate is it?
How a reference is built
MGRS starts from UTM: the world between 80° S and 84° N is split into 60 zones of 6° of longitude and 20 latitude bands of 8° lettered C to X (X is 12° tall). Each zone is divided into 100 km squares named by a column letter and a row letter, which repeat every 2,000 km of northing. The digits that follow are the easting and northing inside the square, with the same number of digits for each: 5 + 5 digits give 1 m, 4 + 4 give 10 m, and so on up to the bare 100 km square.
A reference names a square, not a point
The digits are truncated, never rounded, so a reference always names the square the point lies in, and its south-west corner is the position the digits spell out. This tool draws the square and gives its centre, which is the best single point for the reference: a 6-digit reference such as "18T WL 807 046" can be up to about 70 m from the centre of its 100 m square.
Formulas and checks
Latitude and longitude are converted to UTM and back with Krüger's series to the fourth order on the WGS84 ellipsoid, which is accurate to well under a millimetre inside a zone. The results were compared with PROJ on 50,000 random points: the round trip from a position to a 1 m reference and back always lands inside the 1 m square, and the corner coordinates agree with PROJ to better than 0.000001 m. USNG uses NAD83, which differs from WGS84 by about a metre in the United States, less than the resolution of most references.
Good to know
The band letter matters
The 100 km row letters repeat every 2,000 km, so the latitude band after the zone number decides which repetition is meant. A reference with the wrong band letter is either rejected or lands about 2,000 km away. Check that the band agrees with where you expect the point to be, for example T for New York and U for Germany.
Norway, Svalbard and zone edges
Zone 32V is widened to cover western Norway, and around Svalbard zones 32X, 34X and 36X do not exist. Squares at a zone edge are cut by the zone boundary, and a reference written in the neighbouring zone is still valid; the panel says so when that is the case.
No polar references
North of 84° N and south of 80° S, MGRS uses the polar stereographic UPS grid with zones A, B, Y and Z. This converter does not handle those areas and says so instead of guessing.
Frequently asked questions
How do I convert MGRS to latitude and longitude?
Type or paste the reference, for example 32V NJ 55736 23104 or 32VNJ5573623104, and press "Show". The panel shows the centre of the square in decimal degrees and in degrees, minutes and seconds, each with a copy button.
How do I find the MGRS grid reference of my location?
Press "Use my location" or click the spot on the map. The panel shows the reference at the precision you choose, from 10 digits (1 m) down to the 100 km square, with and without spaces.
Is USNG the same as MGRS?
Yes, for practical purposes. The US National Grid uses the same zones, letters and digits as MGRS, on the NAD83 datum instead of WGS84. In the United States the two differ by about a metre, so this converter reads and writes both.
How many digits should an MGRS reference have?
Ten digits locate a 1 m square, eight a 10 m square, six a 100 m square and four a 1 km square. Search and rescue usually uses 8 or 10 digits; a 6-digit reference is common on paper maps.
Can I convert many MGRS references at once?
Yes. Open "Convert a list", paste one reference or one latitude/longitude pair per line and press "Convert list". The points appear on the map, and the CSV download has latitude, longitude, MGRS and UTM for every line, with an explanation for lines that could not be read.
Something wrong or missing? E-mail [email protected] and it will be fixed.