2.5 Extent (Required)
Purpose and Scope
This element indicates the extent and the physical nature of the materials being described. This is handled in two parts, a number (quantity) and an expression of the extent or material type. The second part of the Extent Element may be either:
- the physical extent of the materials expressed either as the items, containers or carriers, or storage space occupied; or
- an enumeration of the material type(s), usually physical material type(s), to which the unit being described belongs. Material types may be general or specific.
Repositories should establish a consistent method of articulating statements of extent.
If the description of particular media or individual items requires more detail, such as other physical characteristics or dimensions, consult an appropriate standard, such as those listed in Appendix B.
If the material type has been provided in the title statement, do not repeat it in the statement of extent.
Commentary: It is important to include information about the quantity and physical nature of the materials for several reasons. It enables users to eliminate material that is irrelevant to their needs; for example, a user may want only the material containing photographs. It also enables users to plan their research: knowing the quantity is important because it takes longer to go through thirty boxes or twenty hours of sound recordings than it does to go through one box or five hours. The amount of detail provided at any level of description is a matter of institutional policy, depending on user needs and available resources. At lower levels in a multilevel description, extent may be expressed as an enumeration of boxes or folders rather than as a narrative extent statement.
Further details about quantity and physical characteristics may also be provided in the Scope and Content Element (3.1).
2.5.1 Record information about physical characteristics that affect the use of the unit being described in the Physical Access Element (4.2).
Sources of Information
2.5.2 Derive the information from the materials themselves or take it from transfer documents, published descriptions, or other reliable sources.
2.5.3 Record the numerical quantity associated with each expression of physical extent, containers or carriers, number of items, or material type, using the imperial system of measurement in Arabic numerals, unless the repository has made a decision to use the metric system.
2.5.4 Record the quantity of the material in terms of its physical extent as linear or cubic feet, number of items, or number of containers or carriers.1
45 linear feet
2 film reels
10.0 cubic feet
2.5.5 Optionally, record the quantity in terms of material type(s). Material types may be general, such as textual materials,2 graphic materials, cartographic materials, architectural and technical drawings, moving images, and sound recordings, or more specific types, such as those found in RDA and various thesauri.3
10 boxes of textual materials
50 technical drawings
2.5.6 Optionally, qualify the statement of physical extent to highlight the existence of material types that are important.
45 linear feet, including 200 photographs and 16 maps
3 boxes, including photographs and audiocassettes
Multiple Statements of Extent
2.5.7 If a parallel expression of extent is required or desirable, add this information in parentheses.
2,400 photographs (12 linear feet)
89.3 linear feet (150 boxes and 109 oversize folders)
71 maps (3.5 cubic feet)
1 diary (352 pages)
52 megabytes (1,180 computer files)
0.5 linear feet (51 floppy discs, 5 Zip discs, 3 CD-ROMs)
2.5.8 Optionally, provide multiple statements of extent to highlight the existence of material types that are important.
12 linear feet of textual materials, 68 photographs, 16 architectural drawings
107 boxes, 4 oversize boxes, 575 oversize folders, 225 rolled drawings
Approximately 390 linear feet
Two expressions of the extent from the same collection
Approximate Statements of Extent
2.5.9 If parts of the material being described are numerous and the exact number cannot be readily ascertained, record an approximate number and indicate that it is an estimate.
approximately 35 linear feet
about 24,000 maps
circa 11,000 photographs
Statements of Extent for Electronic Records
2.5.10 Electronic records may be described in terms of size (kilobytes, megabytes, gigabytes) or in terms of structure (digital files, directories, items, etc.). If desired, both may be used.
3 file directories containing 48 PDF files
23 digital files (1 Gigabyte)
approximately 275 digital image and audio files (12.4 GB) on 1 portable hard drive
2.5.11 Optionally, descriptions of electronic records may include file format type as well as size. The file format type is normally the file name extension (.doc, .pdf, .ppt, etc.). This is especially recommended where the description includes a link directly to the record.
PDF (88 Kilobytes)
 It is recommended, though not required, that terms reflecting physical extent be spelled out rather than abbreviated, as abbreviations may not be understood by all users.
 It is usually assumed that archival materials are textual in nature, so it may not be necessary to supply the term “textual materials” unless it is desirable to distinguish from other material types.
 See especially Art & Architecture Thesaurus and Library of Congress Authorities (full citations provided in Appendix B).