Setting a reference scale for a 2D map adjusts the size of symbols and text to the desired height and width at that scale. As you zoom in and out, the symbols and text increase or decrease in size accordingly. When no reference scale has been set (the default), symbol and text sizes remain the same on the map as you zoom in and out.
To set a reference scale, compete the following steps:
- Right-click the name of the map in the Contents pane and click Properties.
- On the Map Properties dialog box, on the General page, expand the Reference scale drop-down list and choose a value or provide a value.
To use the current map scale, right-click the name of the map to open the map's context menu, and click Set Reference Scale
. From this menu, you can choose Clear Reference Scale
or Zoom To Reference Scale 
to return the view from other map scales.
Setting a reference scale is useful if you want the detail in the map to look the same as it does on-screen when printed. Using a reference scale means the map symbols appear on-screen at the size they will appear on the printed map. For example, if you are creating a map for publication that will be printed at a scale of 1:25,000, set the reference scale to 1:25,000. You can zoom in on areas with a lot of detail and labeling and assess whether to adjust the symbol sizes or text.
When a reference scale is set, all feature symbology and labels in the current map are scaled relative to the reference scale by default. To disable scaling for individual layers, double-click the name of the layer in the Contents pane to open the Layer Properties dialog box, click the Display tab, and uncheck Scale symbols when a reference scale is set.
While reference scales are useful for designing printed maps, you may want to disable the reference scale when working with interactive and web maps. Typically, a multiscale web map uses symbol and text sizes that are uniquely scaled to each map scale.