The accuracy of an MGRS coordinate lies in the number of digits after the 100 km square. Each extra pair of digits makes the position ten times more precise. Knowing what the digits mean prevents misunderstandings — and unnecessarily long codes.
The precision overview
| Digits (E+N) | Example | Precision | Typical use |
|---|---|---|---|
| 0 | 31U ET | 100 km | Area / zone designation |
| 2 (1+1) | 31U ET 1 6 | 10 km | Rough region |
| 4 (2+2) | 31U ET 12 67 | 1 km | Village / large object |
| 6 (3+3) | 31U ET 123 678 | 100 m | Reference point |
| 8 (4+4) | 31U ET 1234 6789 | 10 m | Building / intersection |
| 10 (5+5) | 31U ET 12345 67890 | 1 m | Exact point |
How to read off the precision
Count the digits after the two letters and divide by two: that is the number of digits per axis. A 6-digit coordinate (3 easting + 3 northing) gives 100 meter precision. Important: a coordinate with fewer digits does not refer to a point, but to a square of that size.
Which precision do you choose?
More is not always better. To point out an area, 4 digits is enough; for a landing zone or target point you use 8 or 10 digits. Choose the precision that matches the reliability of your source — a position from your phone GPS, for example, is rarely accurate to the meter, so 10 digits would then suggest false certainty.
Consistent precision in MilMap
MilMap shows MGRS coordinates in an adjustable precision and keeps it consistent throughout the app and in exports. That way everyone who works with your map or route book knows exactly how precise a position is meant to be.