How To: Convert Decimal Minutes to Decimal Degrees using the Field Calculator


This article pertains to ArcGIS versions 8.x and 9.x. Later versions of ArcGIS may contain different functionality, as well as different names and locations for menus, commands and geoprocessing tools.

Support for Visual Basic for Applications (VBA) for ArcMap and ArcCatalog ended with the ArcGIS 10.2.2 release, and Esri has not included VBA compatibility setups since version 10.5. See: ArcGIS Desktop and VBA Moving Forward.

Instructions provided describe how to convert decimal minutes data to decimal degrees (DDEG) data. This script works for string decimal minutes values in the format of: <Deg> <space> <Decimal_minutes>.
For example:

-10  30.57
100  49.3
  0  25.2789
 45  0
 -2  0.25


  1. Create a new field with data type double to store the DDEG data.
    1. Click Options in the table where the field will be added.
    2. Click Add field.
    3. Type the name of the field.
    4. Click the Type drop-down arrow and select Double.
    5. Click OK.
  2. Select Editor > Start Editing from the Editor toolbar.
  3. Right-click on the new field and select Calculate Values.
  4. Click the Advanced check box.
  5. Copy the following code into the Pre-Logic VBA Script code:
if IsNull(dec_min) or dec_min = "" or IsEmpty(dec_min) then
  dec_deg = 0
  space_pos=InStr(dec_min," ")
  if deg < 0 then
    dec_deg=(Abs(deg)+min) * -1
  end if
end if
  1. On line 1 of the code sample, change [dec_min] to be the name of the field that stores the decimal minutes values.
  2. Type the word dec_deg in the text box under [Your field Name] =.
  3. Click OK.