--- title: "MGRS and UTM Grid Reference Explainer | North Pinnacle" description: "Paste an MGRS or UTM grid reference and see what every part means: zone, latitude band, 100 km square, easting, northing and precision, with diagrams." url: https://northpinnacle.top/grid-reference-explainer/ --- Sheet 5 · Grid references # What does this grid reference mean? Paste an MGRS or UTM reference, or a latitude and longitude, and every part of the grid reference is taken apart and explained. ## Breakdown 31 U D Q 48251 11932 1. ### UTM zone Zone 31 is a 6° strip of longitude from 0° to 6°E. Its central meridian, 3°E, is given the easting 500,000 m, so eastings never go negative. 2. ### U Latitude band Band U covers 48°N to 56°N. Bands are 8° tall and lettered C to X from south to north, skipping I and O; N is the first band north of the equator, so this point is in the northern hemisphere. 3. ### D 100 km column Column D is the 4th letter of this zone's set (ABCDEFGH), so the square starts 400,000 m east of the zone's false origin. Zones cycle through three sets of column letters. 4. ### Q 100 km row Row letters repeat every 2,000 km of northing. Q is position 15 in this zone's sequence (ABCDE…, starting at A because zone 31 is odd), and the band letter says which 2,000 km block applies: the square's south edge is at northing 5,400,000 m. 5. ### Easting within the square 48,251 m east of the square's west edge, written with 5 digits. 6. ### Northing within the square 11,932 m north of its south edge. Easting always comes first: "read right, then up". With 5 digits per coordinate the reference names a **1 m** square, and the point lies somewhere inside it: MGRS truncates, it does not round. Zone 31, band U among the 60 zones and 20 bands Inside square DQ: 10 km grid lines and the 1 m square ### Same point, every precision | Digits | Reference | Square | | --- | --- | --- | | 0 | 31U DQ | 100 km | | 1 | 31U DQ 4 1 | 10 km | | 2 | 31U DQ 48 11 | 1 km | | 3 | 31U DQ 482 119 | 100 m | | 4 | 31U DQ 4825 1193 | 10 m | | 5 | 31U DQ 48251 11932 | 1 m | ## Reading a grid reference An MGRS reference has three parts. The **grid zone designator** (31U) names a cell of the UTM grid: one of 60 zones, each 6° of longitude, and one of 20 latitude bands lettered C to X. The **100 km square identifier** (DQ) is a column letter and a row letter. The **numerical location** (48251 11932) gives the easting and then the northing inside that square, always as two halves of equal length. The number of digits sets the precision: one digit each pins a 10 km square, two a 1 km square, three 100 m (the familiar six-figure reference), four 10 m and five 1 m. References are truncated, so the point lies inside the square named and never in a neighbouring one. Read the digits "right, then up": easting first. UTM writes the same position in full metres: zone, hemisphere, easting and northing. The letters in MGRS are only a shorthand for the hundreds-of-kilometres digits. Two places break the regular grid: zone 32V is widened to cover south-west Norway, and zones 31X to 37X over Svalbard are 9° or 12° wide, with 32X, 34X and 36X left out. ## Digits and squares - 2 digits (1 + 1): 10 km - 4 digits: 1 km - 6 digits: 100 m - 8 digits: 10 m - 10 digits: 1 m ## Sources - National Geospatial-Intelligence Agency. *The Universal Grids and the Transverse Mercator and Polar Stereographic Map Projections*, NGA.SIG.0012_2.0.0_UTMUPS (2014), [NGA Office of Geomatics](https://earth-info.nga.mil/). - Veness C. [UTM coordinates and MGRS grid references](https://www.movable-type.co.uk/scripts/latlong-utm-mgrs.html), Movable Type Scripts, on the column and row lettering and the Norway and Svalbard exceptions. - [Military Grid Reference System](https://en.wikipedia.org/wiki/Military_Grid_Reference_System): an overview of grid zone designators, 100 km square identifiers and precision. ## Questions **What is the difference between UTM and MGRS?** None in position: MGRS is UTM with the leading digits of easting and northing replaced by two letters, which makes references shorter and easier to read out over a radio. **Can I enter a British or Irish national grid reference?** No. Those grids look similar (SU 12345 67890) but use different projections and datums. Convert them to latitude and longitude with a national mapping agency's tool first. **Why does the square letter change when I move a few metres?** You crossed a 100 km grid line. The letters change and the digits restart from 00000; the two references are still only metres apart.