I would like to calculate the lenght(km) of each line in shapefile of roads in a study area. I tried to use "Calculate Geometry" but it doesn't work! I cannot select 'Units', and 'Property' for 'Length' is "Length - Disabled" in Calculate Geometry dialog.

How can I calculate length of roads?

Coordinate system is WGS84.

  • 1
    We can't read your mind. Be more precise!?
    – Frodo
    May 23, 2020 at 12:17
  • What are the units of your shapefile’s coordinate system?
    – PolyGeo
    May 23, 2020 at 19:15
  • coordinate system : WGS 1984
    – Jalal
    May 23, 2020 at 21:36

2 Answers 2


In "Calculate Geometry" dialog, calculating length is disabled for line shapefile which is in Geographic Coordinate System (GCS). The same thing happens when you try to calculate area and perimeter for polygon shapefile which is in GCS.

You need to project WGS84 into a Projected Coordinate System (PCS). Or you can specify a PCS for Data Frame and then select that PCS as "Use coordinate system of the data frame" in "Calculate Geometry" dialog.

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You can use 'Calculate Geometry' which will get you lengths in metres and then create a new field and use 'Field Calculator' to divide the values in first column by 1000. [Name of field contains values in metres] / 1000

  • Thank you for your reply, but i couldn't understand why in property of Calculate Geometry " Length Disabled" ??
    – Jalal
    May 23, 2020 at 14:33

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