When you draw maps within a data frame, you can display the map at any desired map scale. You can also set up a series of desired map scales that allow you to select a map scale from a list.
You can specify the scale of your map by either typing in a value or choosing one from a list.
Scale entry can be flexible. There are many ways you can enter values into the scale box.
- You can simply type a number with or without comma separators.
- You can type a 1: and a number.
- You can paste values into the box.
- You can type a relative scale (e.g., 1 cm = 100 m or 1 in = 1 mi).
- The 1: prefix can be present or absent (e.g., 1,000,000).
- A hyphen (-) or the word to can be used as the separator in place of a colon (:).
- Commas used for separating thousands can be present or absent (e.g., 1,000,000 or 1000000).
- The values in absolute scale expressions can be specified in reverse order (e.g., 5 mi to 1 in).
- The number one can be given as a number or a word (e.g., One inch = 5 miles)
- The following unit abbreviations can be used:
in, pt, ft, yd, mi, nm, mm, cm, m, km, dd, dm
- Plurals can be used or not (e.g., mile or miles).
You will see two additional options in the Scale drop-down list when you are specifying a scale on a dialog box:
- <None>: Choose this option to clear the scale so that no scale is used. As a shortcut to choosing <None> from the list, you can type 0, none, or <None>.
- <Use Current Scale>: If you choose this option, the current scale of the active data frame as it is displayed in the current view will be automatically inserted into the field. This makes it very easy to set the scale to be the same as the current scale you are using. So if you choose this option when the current scale of the data frame in your map is 1:45,678, that value will appear in the scale field.
Customizing the map scale list
You can customize the standard scales that appear in the map scale list throughout ArcMap, along with the format with which scales are shown.
Using <Customize This List...>
When you click on Customize This List from the Scale drop-down list, the Scale Settings dialog box appears that allows you to build a series of map scale settings and to use a map scale list prepared by others.
You can add and remove map scales by manually typing them or by clicking Add Current to add the current map scale to the list.
You can also save your scale settings and share them with other users or load a scale settings file for use on your maps.
Changes you make to the list of standard scales on the Standard Scales tab are stored in the active data frame in your map. Each data frame in your map document can have a different list of standard scales. In this way, you can tailor the list of standard scales to the specific map represented by each data frame in your map document. To make your current set of standard scales the default that will be used in all new map documents you create, click the Set As Default button on the Standard Scales tab. To reset your active data frame to use the default of standard scales, click Load > Default Scales.
You can limit the map display to the scales listed by checking the Only display these scales when zooming check box. When this box is checked, zooming in using any method that steps progressively through scales will be limited to the scales listed in this dialog. This option applies to rolling the mouse wheel, clicking the Fixed Zoom In 
and Fixed Zoom Out 
buttons on the Tools toolbar and pressing the + or – keys on your keyboard. By default it doesn't apply to the interactive Zoom In 
and Zoom Out 
tools on the Tools toolbar.
You can also set how map scales appear using the Scale Format tab on the Scale Settings dialog box.
When creating or editing scale formats, you will have different options available depending on whether you are working with an absolute or relative scale format. For an absolute format, you can set the separator to use in the scale ratio. By default, a colon is used. For a relative format, you can set both the page and map units (for example, centimeters on the page equals miles on the ground), specify the equals indicator, and set appearance options such as the number of decimal places to show and whether to capitalize or abbreviate the units. You can also specify whether to Show thousands separators (for example, 24000 has no separators) or to Reverse the order of the scale (for example, 24,000:1).
Changes you make on the Scale Format tab are stored at the application level and apply to all your ArcMap sessions. The scale format information is not stored inside your map document.