What is UTM and why is it used?

UTM (Universal Transverse Mercator) is a cylindrical map projection that divides the Earth into 60 north–south zones each 6° wide. Unlike geographic latitude/longitude, UTM gives you flat Cartesian metre coordinates, so you can measure straight-line distances and areas with simple arithmetic. It is the coordinate system used on most topographic maps, GPS receivers, military grid references (MGRS), and GIS software.

How accurate is the conversion?

The tool implements the full Transverse Mercator series expansion from USGS Professional Paper 1395 (Snyder 1987). Within the standard UTM valid region — up to ±3° from the central meridian — accuracy is sub-millimetre. Accuracy degrades smoothly for points farther from the central meridian, but the projection is rarely used there in practice.

What is the difference between easting, northing and zone?

The zone number (1–60) tells you which 6° longitude band the point lies in. The easting is the distance in metres east of a false origin set 500 000 m west of the central meridian, so it is always between roughly 100 000 m and 900 000 m. The northing is the distance in metres north of the equator (northern hemisphere) or of a false origin 10 000 000 m south of the equator (southern hemisphere), ensuring the northing is always positive.

What does the zone letter mean?

The UTM latitude band letter (C through X, skipping I and O) divides each zone into 8° latitude bands. Together with the zone number it is sometimes written as a single grid designator, e.g. "30U" for London. The letter is purely informational in this tool — the actual projection uses the hemisphere (N/S) switch, not the letter, to determine the false northing.

Does this tool handle the special zones around Norway and Svalbard?

Yes. The converter applies the standard exceptions defined in the UTM specification. Zone 32 is extended westward to cover southwest Norway (56°N–64°N, 3°E–12°E), and four irregular zones (31, 33, 35, 37) cover Svalbard above 72°N so that the ice-cap landmass is not split across zone boundaries.

Can I use this for MGRS (military grid) coordinates?

MGRS builds on UTM by adding a 100 km grid square letter pair on top of the zone designator. This tool gives you the UTM zone, easting and northing — you can then look up the 100 km square identifier in a standard MGRS table. Full MGRS encoding (square lookup) is outside this tool's scope, but the UTM output is the correct input for MGRS converters.

UTM Coordinate Converter

The UTM Coordinate Converter translates between WGS-84 geographic coordinates (latitude and longitude in decimal degrees) and Universal Transverse Mercator grid references (zone, easting, northing) in both directions. It is aimed at hikers using paper maps, GIS analysts needing quick sanity-checks, developers building location-aware apps, and anyone who receives a set of UTM coordinates and needs to locate them on a modern map.

How it works

UTM is a Transverse Mercator projection applied to 60 successive 6° longitude zones, numbered 1 (starting at 180° W) through 60. Within each zone the projection rolls the ellipsoid onto a flat cylinder aligned with the zone’s central meridian. Because the cylinder is tangent along that meridian, scale distortion is minimal near the centre and acceptable up to ±3° away.

The tool uses the WGS-84 reference ellipsoid (semi-major axis a = 6 378 137 m, inverse flattening 298.257223563) and the standard UTM parameters:

Scale factor at the central meridian: k₀ = 0.9996
False easting: 500 000 m (so all eastings are positive)
False northing: 0 m (northern hemisphere) or 10 000 000 m (southern hemisphere)

Geographic → UTM

Given latitude (phi) and longitude (lambda), the algorithm:

Determines the zone from the longitude: zone = floor((lon + 180) / 6) + 1, then applies the standard exceptions for southern Norway and Svalbard.
Computes the central meridian longitude: lon_CM = (zone - 1) * 6 - 180 + 3 degrees.
Evaluates the meridian arc length M to the point’s latitude using the Helmert series.
Computes the transverse Mercator easting and northing from the standard fifth-order series expansions in terms of N (radius of curvature in the prime vertical), T (tan²phi), C (e’²cos²phi) and the longitude offset A = cos(phi)(lambda - lambda_CM).

UTM → Geographic

The inverse starts from the point’s reduced northing y = N - N₀ (N₀ is the false northing), recovers the meridian arc M₀ = y / k₀, then iterates Newton’s method five times to find the footprint latitude phi₁ such that M(phi₁) = M₀. The final latitude and longitude follow from the standard inverse series using the radii of curvature at phi₁.

Worked example

London (Big Ben) → UTM

Input: 51.5007°N, 0.1246°W (i.e. lat = 51.5007, lon = −0.1246)
Zone: 30U (central meridian 3° W)
Easting: 699 338 m
Northing: 5 710 059 m

To reverse: enter zone 30, Northern hemisphere, easting 699 338, northing 5 710 059 → get back 51.5007°N, 0.1246°W.

Location	Lat	Lon	Zone	Easting	Northing
London	51.5074	-0.1278	30U	699 328	5 710 154
New York	40.7128	-74.0060	18T	583 960	4 507 523
Sydney	-33.8688	151.2093	56H	334 116	6 252 078
Nairobi	-1.2921	36.8219	37M	261 378	9 857 215

All conversions are performed entirely in your browser — no data is sent to any server.

Formula note

The series used here matches Snyder (1987) USGS PP-1395 §10 (Transverse Mercator) to fifth order in the longitude offset, which gives centimetre-level accuracy at the zone boundary and sub-millimetre accuracy near the central meridian. For the highest-precision geodetic work (sub-micrometre requirements), Karney (2011) Transverse Mercator with sub-arcsecond accuracy extends the series to arbitrary order; the practical difference for any real-world field use is negligible.