Problem: The Measure tool is disabled in ArcMap
When accessing the Tools toolbar in ArcMap, the Measure tool is disabled (grayed out).
This issue occurs because the map does not have known units.
Solution or Workaround
Set the map unit of the data frameSet the map unit of the data frame with a known unit such as Meters or Miles.
Note: The map units are determined by the data frame's coordinate system.
Specify a coordinate system
1. Specify a coordinate system for the data frame.
2. After the coordinate system of the data frame is specified, the map unit is also set with a known unit.
Note: The data frame's coordinate system is usually determined by the first layer added to the map. Apply a projected coordinate system (PCS) to measure areas. For more information on changing and assigning a coordinate system, refer to Specifying a coordinate system.
- ArcGIS Help: Define Projection
- ArcGIS Help: Coordinate systems for map display
- Technical Article: How to identify an unknown projected coordinate system using ArcMap