What Is UTM? (And How to Convert It to Lat/Long)
UTM gives a position in metres east and north inside one of 60 zones. What the numbers mean, why field teams use them, and how to convert UTM to lat/long.
UTM (Universal Transverse Mercator) gives a position as metres east and metres north inside one of 60 zones that divide the world. A UTM coordinate like 18M 349027 9283255 means zone 18, band M, 349,027 metres east and 9,283,255 metres north, which is a point near Tarapoto, in the Peruvian Amazon.
To turn a UTM coordinate into latitude and longitude, paste it into our free UTM to Lat/Long Converter. It also converts back, and shows the point on a map so you can check it.
What do the numbers in a UTM coordinate mean?
A UTM coordinate has four parts. Take 18M 349027 9283255:
| Part | Example | What it means |
|---|---|---|
| Zone | 18 | Which of the 60 zones, each 6° of longitude wide |
| Band or hemisphere | M | A latitude band letter, or N/S for the hemisphere |
| Easting | 349027 | Metres east, measured from 500,000 at the zone's centre line |
| Northing | 9283255 | Metres north of the equator; in the south, counted down from 10,000,000 |
Two details trip people up. The easting is never zero: the zone's centre line is set at 500,000 so no point inside it goes negative. And in the southern hemisphere the equator is 10,000,000, so a site 6.5° south of the equator has a northing above 9,280,000.
The same point in latitude and longitude is -6.4825, -76.3653, or 6°28'57" S, 76°21'55" W.
What are UTM zones, and which one am I in?
The world is cut into 60 zones, each 6° of longitude wide, numbered eastward from 180° W. Zone 1 starts in the Pacific; zone 18 covers 78° W to 72° W, which takes in much of Colombia and Peru.
To find your zone, add 180 to your longitude, divide by 6, round down and add 1. For Tarapoto: (-76.37 + 180) / 6 = 17.3, so zone 18. Or click the spot on the converter's map and read it.
Many countries span several zones. Peru uses 17, 18 and 19; Costa Rica 16 and 17. Projects with sites on both sides of a zone line should agree on one zone, or on latitude and longitude, before the first data comes in.
Does the letter after the zone mean north or south?
It depends on who wrote it, and it is the easiest UTM mistake to make.
- In the standard notation, the letter is a latitude band, 8° tall (X, the northernmost, is 12°), from C in the far south to X in the far north (I and O are skipped). C to M are south of the equator; N to X are north.
- Many people and devices write N or S for the hemisphere instead.
So 18S can mean band S, between 32° and 40° north, or "zone 18, south". Lima is 18S 277617 8667488 in the second sense. Read the S as a band, or write it as 18N, and the same numbers land at 78° north, in the Canadian Arctic.
The converter shows how it read the letter and lets you switch between north and south.
Why do field teams use UTM instead of latitude and longitude?
Because it is in metres. Two trees with the same northing and eastings of 349027 and 349037 are 10 metres apart; no trigonometry needed. That makes UTM easy for laying out plots, pacing distances and checking spacing on the ground.
It is also what many tools give you. Handheld GPS units often display UTM, topographic maps print a UTM grid, and survey and cadastral data often arrive in a grid of metres: UTM or a national grid like Costa Rica's CRTM05.
Latitude and longitude are better for sharing. They work everywhere without a zone, and web maps, GeoJSON and phone apps expect them. Most projects end up with both: UTM from the field and the old surveys, latitude and longitude for the maps and the reports.
How do you convert UTM to latitude and longitude?
- Open the UTM to Lat/Long Converter.
- Paste the coordinate with its zone and letter, for example
18M 349027 9283255. Decimal degrees and degrees-minutes-seconds work too. - Copy the latitude and longitude in the format you need, and check the point on the map.
Clicking anywhere on the map gives you that spot in all three formats. The conversion runs in your browser; nothing is uploaded.
For a whole spreadsheet, use a GIS tool: in QGIS, load the table as a delimited text layer in its UTM coordinate system, then export it in WGS84 (EPSG:4326).
Why does my converted point land in the wrong place?
Check these, in order:
- The hemisphere. A point thousands of kilometres north or south of where it should be has the wrong letter. Switch north and south.
- The zone. A point a few hundred kilometres east or west is in the neighbouring zone. A spreadsheet with only eastings and northings has lost its zone; ask which one the team used.
- Easting and northing swapped. The easting is the shorter number (six digits), the northing the longer one (up to seven).
- The datum. Older maps and surveys use other datums. In Peru, coordinates on the old PSAD56 datum sit roughly 400 metres from the same numbers read as WGS84. The point looks almost right, which is why this one survives longest.
Once the points are in latitude and longitude, they can go into a map or a GeoJSON file. If you are working with shapes rather than points, see WKT vs GeoJSON.
Frequently asked questions
What is the difference between UTM and latitude/longitude?
Latitude and longitude give a position in degrees on the whole globe. UTM gives it in metres east and north inside one of 60 zones. Both can describe the same point; UTM just needs the zone and hemisphere to make sense.
How many digits does a UTM coordinate have?
The easting has six digits (between about 166,000 and 834,000 metres at the equator). The northing has up to seven (0 to about 9,300,000 in the north, 1,100,000 to 10,000,000 in the south). Decimals below a metre are rarely meaningful for field data.
Can I measure distances between UTM points in different zones?
Not directly. Each zone has its own grid, so the numbers jump at the zone edge. For a project that crosses a zone line, pick one zone for the whole project or work in latitude and longitude.
What datum does the UTM to Lat/Long Converter use?
WGS84, the datum GPS receivers and phones use. If your coordinates come from an older map or survey on another datum, convert the datum in a GIS tool first.
How do I convert UTM to latitude and longitude for free?
Paste the coordinate, for example 18M 349027 9283255, into the free UTM to Lat/Long Converter from Restoration Scope. It shows decimal degrees and degrees-minutes-seconds, places the point on a map, and runs in your browser.
