Getting zone from UTM in order to convert to latlong

I am trying to convert UTM to a latlong point. To get that done I need to know the zone where the UTM coordinates are. how can I find the zone from UTM?. the place coordinates that I work on lay on zone 39 and 40.

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In general, you cannot determine the zone from the coordinates: that's why the zone is needed!

In your case, though, it sounds like you are looking within a small area that straddles neighboring zones. In that case, locations in zone 39 will have large positive x-values and locations in zone 40 will have negative or small positive x-values: that's how you can tell them apart. This approach will work provided your area does not extend more than six degrees in longitude from east to west (the width of one zone). (In general, compute the longitude using both zone options and choose the one that falls within your area of interest.)

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On a matter of pedantry, UTM zones have a false easting big enough to cover quite a lot of the westward neighbour, so it is unlikely x-values will be negative, just nearer zero. But your assertion still stands. – MerseyViking Apr 13 '12 at 15:04
Thanks @Mersey, I had forgotten about that. I had better edit the reply. – whuber Apr 13 '12 at 15:05
sounds nice to work out the LatLong boundaries for the place and try 39 and check the result if it lands in the specified boundaries. if not try 40. thanks a lot. – Sami Al-Subhi Apr 13 '12 at 15:30

You can identify the zone on this map: http://www.theartofdredging.com/utmzones.htm

Once you find your zone, then you can easily convert the UTM coordinates to any coordinates using http://www.hamstermap.com.

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