GPS coordinates: decimal → DMS
Enter latitude and longitude in decimal degrees (as from Google Maps): get the degrees-minutes-seconds format.
What it's for
Online maps give coordinates in decimal degrees (e.g. 41.9028, 12.4964), but many GPS units and nautical/aviation tools use degrees-minutes-seconds. This tool converts.
How to read them
41°54'10"N means 41 degrees, 54 minutes and 10 seconds North of the equator. Longitude indicates East (E) or West (W) of Greenwich.
Three ways of writing the same point
The same coordinates circulate in three different formats and look like three different places: decimal degrees (41.9028), degrees and decimal minutes (41° 54.168'), degrees minutes seconds (41° 54' 10.1"). The point on the map is identical, only the writing changes.
The degrees and decimal minutes format is the one used at sea and in aviation, which is why it is what charts and chartplotters show. Decimal degrees are what Google Maps and APIs use; degrees minutes seconds are what books and signposts use.
The sign and the letters
In decimal degrees the minus sign does the job of the letters: a negative latitude means South, a negative longitude means West. -33.8688, 151.2093 is Sydney; 33.8688, 151.2093 is a spot in the Syrian desert.
Getting the sign or the order wrong is the commonest and quietest mistake, because the result is always a valid point somewhere in the world. Latitude always comes first and runs from -90 to +90; longitude from -180 to +180. If a number is above 90, it is not the latitude.
What one decimal is worth
On latitude the sums are easy: one degree is about 111 km, one minute about 1.85 km (the nautical mile), one second about 31 metres. In decimal degrees, the fourth digit after the point is worth some ten metres: that is the precision needed to find a front door.
On longitude the same digit is worth less and less as you move towards the poles, because the meridians converge: at the equator a degree is 111 km, in Rome about 82, in Oslo about 50. That is why a difference in longitude cannot be turned into metres without knowing the latitude you are at.
Nearby tools
For the straight-line distance between two points there is Distance between cities, and for the local time World clock. If you want the coordinates to work out where a photo was taken, see Photo EXIF data.