How Do You Convert Latitude and Longitude to Decimals?
To convert latitude and longitude to decimal notation, you must find the degrees, divide the minutes by 60 and divide the seconds by 3,600. Finally, add these three numbers together, and determine if the answer is positive or negative.

Find the degree of the latitude or longitude
As an example, in the latitude 119 degrees 30 minutes 20 seconds, more commonly written as 119° 30′ 20”, the degree is 119.

Place the degrees before the decimal point
In decimal notion, the example should be written as 119.00 degrees.

Divide the minutes by 60
There are 60 minutes in one hour. Therefore, divide the number of minutes in the latitude or longitude by 60. In the example, the latitude has 30 minutes. Divide 30 by 60 to get 0.5. Add 0.5 to your degrees. 119.00 plus .5 is 119.5 degrees.

Divide the seconds by 3,600
There are 3,600 seconds in one hour. Divide the number of minutes in the latitude or longitude by 3,600. In the example, the latitude has 20 seconds. Divide 20 by 3,600 to get 0.0055555 with a repeating 5. Add this decimal to your previous answers and get 119.50555 degrees.

Determine if the answer is positive or negative
If the latitude or longitude is North or East, the decimal is positive. If your latitude is South or West, the decimal is negative.