About the DMS to Decimal Degrees
Degrees-minutes-seconds (DMS) is the traditional way to write latitude and longitude on nautical charts, land surveys, and older GPS units, but almost every digital mapping tool, from Google Maps to GIS software, expects coordinates as a single decimal number. This tool takes a DMS coordinate apart into its degrees, minutes, and seconds and reassembles it into the decimal degrees format those tools need, so you can paste a chart reading straight into a map search box.
How It Works
Enter the whole degrees, then the minutes and seconds portions as positive numbers. The calculator keeps the sign from the degrees field, converts the minutes to a fraction of a degree by dividing by 60, and converts the seconds to a fraction of a degree by dividing by 3600, then adds the three pieces together. The result is displayed as a single decimal degrees value rounded to six decimal places.
Formula & Methodology
For 40 degrees 26 minutes 46 seconds, divide 26 by 60 to get 0.433333 degrees, divide 46 by 3600 to get 0.012778 degrees, then add both to the whole 40 degrees for a total of 40.446111 decimal degrees. For a southern or western coordinate, apply the negative sign to the degrees value only, since minutes and seconds are always entered as positive magnitudes.
Examples
Statue of Liberty latitude
Entering 40 degrees, 26 minutes, and 46 seconds returns 40.446111 decimal degrees, the standard way that coordinate would appear in a GPS app or web map.
A western longitude
For a longitude of negative 73 degrees, 59 minutes, and 9 seconds, the calculator keeps the negative sign from the degrees field and returns -73.985833 decimal degrees.
Advantages
- Removes the manual arithmetic of dividing minutes by 60 and seconds by 3600, a step that's easy to get wrong by hand.
- Produces the exact decimal format that mapping platforms like Google Maps and Google Earth expect for a direct coordinate search.
- Keeps six decimal places of precision, enough to pinpoint a location to sub-meter accuracy at the equator.
Common Mistakes
- Typing a negative sign on the minutes or seconds value instead of the degrees value, which the calculator does not use to flip the overall sign.
- Forgetting to apply the negative sign at all for southern latitudes or western longitudes, since DMS notation usually shows direction rather than a minus sign.
- Entering minutes or seconds values above 59, which produces a numerically valid but non-standard result rather than an error.
Edge Cases to Watch For
- The sign is read only from the Degrees field. If you type a negative number into Minutes or Seconds instead, the calculator still applies the sign from Degrees and effectively ignores the sign on those fields, which can silently produce the wrong coordinate.
- Minutes and seconds are not range-checked against 60. Entering, say, 75 seconds does not carry over into an extra minute, it is simply divided by 3600 and added, which will give a coordinate that is technically off from a properly normalized DMS reading.
- Output is rounded to six decimal places, which corresponds to roughly 0.11 meters of precision at the equator, more than enough for driving directions or general mapping but coarser than survey-grade GPS.
Common Use Cases
- Pilots and mariners converting chart coordinates given in DMS into decimal degrees for a GPS flight plan or chartplotter waypoint.
- GIS analysts and surveyors cleaning up legacy coordinate data that was recorded in DMS format before importing it into mapping software.
- Hobbyist geocachers and hikers converting a DMS coordinate from an old map or logbook into a format their phone's map app can search.