Check UTM Coordinate by Manfred Egger
Write unknown UTM coordinate in the fields:
X:
Y:
Use Zoom and Pan to find the place, where your unknown UTM coordinate is located:
Map Center: LAT:
LON:
Copyright: Manfred Egger, 2016. Web: http://www.egger-gis.at . This tool is using: https://openlayers.org/.