How to read an MGRS grid reference
MGRS builds on UTM and squeezes a location into one short string. 18T WL 83959 07350 means:
- 18T — the UTM zone and latitude band (the grid zone designator).
- WL — the 100 km square inside that zone.
- 83959 07350 — easting and northing inside the square. Five digits each give 1 m precision, four give 10 m, three give 100 m.
The US National Grid (USNG) uses the same numbers on the WGS 84 / NAD 83 datum, so USNG references convert the same way.
Precision and the corner rule
An MGRS reference names a square, not a point. 18T WL 839 073 is a 100 m square, and by convention the coordinates refer to its south-west corner. When you paste a shortened reference, the converter tells you how big the square is. Read right, then up: easting digits always come first.
Where MGRS is used
Armed forces, search and rescue, wildland fire crews and many emergency services in North America and NATO countries use MGRS/USNG because it is short to read over a radio and works on paper maps with a printed grid.
Accepted input
With or without spaces (18TWL8395907350), in upper or lower case, with 0 to 10 digits as long as the count is even. Zones run from 1 to 60 and bands from C to X, skipping I and O.
Frequently asked questions
What is the difference between MGRS and UTM?
MGRS uses UTM zones and metres but replaces the long easting and northing with a two-letter 100 km square plus short digit groups, so 18T 583959 4507350 becomes 18T WL 83959 07350.
How precise is a 10-digit MGRS reference?
Ten digits (five easting, five northing) identify a 1 metre square. Eight digits are 10 m, six digits 100 m.
Is USNG the same as MGRS?
Yes for practical purposes. USNG is the US civilian version of MGRS and uses the same grid on the NAD 83 / WGS 84 datum.