What inputs does UTM to lat/long need?

It needs the zone number (1 to 60), the hemisphere (north or south), the easting in metres and the northing in metres. The hemisphere is required because northings repeat between the two halves of the globe.

Why does the hemisphere matter so much?

In the southern hemisphere a false northing of 10000000 metres is added so values stay positive. Without knowing the hemisphere, the converter cannot tell whether a northing of 5000000 means the north or south half.

What ellipsoid is assumed?

The WGS-84 ellipsoid is used, matching GPS and most modern datasets: semi-major axis 6378137 metres and flattening 1/298.257223563.

How accurate is the inverse projection?

The Krüger series used here is accurate to sub-millimetre level inside the zone, so the recovered latitude and longitude match the original coordinates to well under a metre.

UTM to Lat/Lng Converter

This tool converts UTM coordinates — zone, easting and northing — back to WGS-84 decimal latitude and longitude. It is the inverse of the lat/long to UTM projection and is useful when a dataset, survey or map gives you metre-based grid references that you need as GPS coordinates.

How it works

The easting has its false easting of 500000 m removed, and in the southern hemisphere the false northing of 10000000 m is subtracted from the northing. The values are divided by the meridian-arc radius and the central-meridian scale factor k0 = 0.9996, then a Krüger inverse series in the conformal coordinates recovers the latitude and longitude offset from the zone’s central meridian:

central meridian = (zone - 1) * 6 - 180 + 3 degrees
longitude = central meridian + recovered offset

The series runs on the WGS-84 ellipsoid, so the result matches GPS coordinates directly.

Tips and notes

Always set the correct hemisphere — a southern-hemisphere northing looks identical to a northern one without it. UTM is valid only between about 80°S and 84°N. The inverse series is accurate to sub-millimetre level inside a zone, so round-tripping a coordinate through both converters returns the original value. Everything runs in your browser.