Labels in ArcMap legend are different sizes

Description

Labels in an ArcMap Legend and in the Legend Item Properties display label text symbols of different sizes.

Cause

Legend item styles store formatting information about legend items, such as label symbol, patch size, arrangement of label, and description text.

When a legend item style is applied to each legend, the formatting information is applied directly to a legend item. This means that regardless of the current formatting of the legend, the information for the target legend item will be overwritten with the formatting information from the legend item style.

The default legend item styles have a label text symbol size of 9 points. Applying one of these legend item styles to an existing legend item in your legend, or adding data to an existing legend, the legend item label changes to 9 points.

Workaround

1. After adding new data, check the label size of the existing legend item: Right-click on the legend and select Properties.
2. In the Legend Properties dialog box select the Items tab. Select the existing item, such as STATES, and click Style.
   
   
3. In the Legend Item Selector dialog box, click Properties.
   
   
4. In the Legend Item dialog box, click the Label Symbol button.
   
   
5. In the Symbol Selector dialog box note the font size, such as 25.15 points. This is the font size we will apply to the new legend item labels.
   
   
6. Click Cancel three times to return to the Legend Item Properties dialog box (same as Step 2).
7. For each new legend item, modify its label size to match the size of the existing items. Refer to steps 2-5 above.
8. Click OK to close the Legend Properties dialog box and apply the changes. All legend item labels are the same size. The legend can be resized and scales correctly.