MILITARY GPS SURVIVAL KIT
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How to Read MGRS Coordinates

A field-manual walkthrough of the Military Grid Reference System: grid zone, 100 km square, and the easting/northing digits — plus how to read a grid to 1 metre and avoid the mistakes that put you in the wrong square.

An MGRS grid reference looks like a wall of characters until you know where to cut it. Once you do, it reads left to right the way a map does: coarse location first, then finer, then finer again. This entry breaks down a single reference and shows how to read one at any precision.

Here is the reference we will use throughout:

11S NA 16477 11316

Four parts, and each one narrows the search.

Grid zone designator
11S
100 km square
NA
Easting
16477
Northing
11316

Part 1 — The grid zone designator

11S is the grid zone designator. It is the coarsest part of the reference and it does two jobs at once.

The number is the UTM zone: one of 60 longitude bands, each 6° wide, counted east from the antimeridian. Zone 1 starts at 180°W, so zone 11 covers 117°W to 111°W.

The letter is the latitude band: 8° of latitude, lettered C through X from south to north. I and O are skipped because they read as 1 and 0. Band S covers 32°N to 40°N.

The letter is not a hemisphere

A common misread: S here does not mean "south". It is a latitude band label. Bands C to M are in the southern hemisphere and N to X are in the northern — so band S is comfortably north of the equator.

Together, 11S puts you in a box roughly 6° by 8°. That is still enormous, so the reference keeps going.

Part 2 — The 100 km square

NA identifies a 100 km by 100 km square inside the grid zone. The first letter is the column, counted eastward; the second is the row, counted northward. The lettering scheme repeats every 18 columns and every 20 rows, which is why the grid zone designator has to come first — NA on its own is ambiguous across the globe.

At this point the reference 11S NA has you inside a 100 km square. Everything that follows splits that square.

Part 3 — Easting and northing

The digits are the position inside the 100 km square. They always split into two equal halves: the first half is the easting, the second is the northing.

DigitsPrecisionExample
210 km11S NA 1 1
41 km11S NA 16 11
6100 m11S NA 164 113
810 m11S NA 1647 1131
101 m11S NA 16477 11316

So in 11S NA 16477 11316, the easting is 16477 and the northing is 11316 — 16 477 metres east and 11 316 metres north of the square's south-west corner.

Split the digits, do not read them as one number

The single most common error is reading 1647711316 as one long string and splitting it in the wrong place. Count the digits first, halve them, then read. An odd number of digits means the reference is malformed — not that one half is longer than the other.

Read right, then up

The order is always east first, then north — "read right, then up" in the Army's phrasing. It matches how the digits are written and how you would walk it on the ground: along the bottom edge, then up.

Part 4 — Precision and trailing zeros

Precision is carried by the number of digits, not by padding. These are not the same place:

  • 11S NA 16 11 is a 1 km square whose corner is at 16 000 m east, 11 000 m north.
  • 11S NA 16000 11000 is a 1 metre square at exactly that corner.

The first is an area; the second is a point. Dropping digits widens the box you are describing, so quote only the precision you actually have. A GPS fix good to ±3 m does not justify a 10-digit reference implying 1 m.

Reading a reference back out

Putting it together, 11S NA 16477 11316 decodes as:

  1. 11 — UTM zone 11, longitude 117°W to 111°W.
  2. S — latitude band S, 32°N to 40°N.
  3. NA — the 100 km square, column N, row A.
  4. 16477 — 16 477 m east of that square's western edge.
  5. 11316 — 11 316 m north of its southern edge.

Which lands in Death Valley, California — about 36.24660° N, 116.81660° W in decimal degrees, or 11N 516478 E 4011316 N in UTM.

Datum matters

Every figure above is on WGS-84. The same grid reference on a different datum can land hundreds of metres away, so check the datum printed on your map before you trust a conversion. Older US topographic sheets often use NAD 27.

Why MGRS instead of latitude and longitude

Lat/long is precise but awkward to speak, write and plot under pressure. MGRS is built for the opposite constraints:

  • It is shorter to transmit — ten digits and four characters beat two signed decimals.
  • It is unambiguous about precision — the digit count states it outright.
  • It plots directly on a gridded map with no conversion arithmetic.
  • It degrades gracefully — drop digits and you still have a valid, coarser reference.

That is the whole system. Zone, square, right, up.