The National Archives Catalog


Mandatory Repeatable Data Type Authority Level Available A/V Only Public Element
Yes* No Variable Character Length (2000) None Series
File Unit
No Yes

*Extent is mandatory at the Series Level only.



The measurement or amount of the archival materials themselves -- the linear measurement, page count, number of rolls, reels, cassettes, or number of data files.

Extent is related to Holdings Measurement Count and Holdings Measurement Type. All are aimed at measuring the intellectual bulk of the archival materials. Extent, being a narrative field, accommodates a wide range of units of measure, such as linear feet, pages, photographs, and so on. The element is meant to clearly communicate the amount of archival materials to the researcher. For these reasons, however, the field cannot be summed. By contrast, Holdings Measurement Type and Holdings Measurement Count, being controlled fields, can be combined to produce NARA-wide statistics about holdings.


Purpose: Informs users of the amount of archival materials available.


Relationship: This element is dependent on Copy Status. Each copy of the archival materials must have a copy status specified to have Extent.



Enter the measurement of the archival materials. Write a simple statement that gives the number of measurement units followed by the units of measure used. Do not use full sentences. If the extent is an estimation, the statement can be preceded by language to indicate that the measurement is estimated. If a number is longer than three digits, use commas. For example, a number should be written out as 12,877 instead of 12877.

Two-dimensional Materials
For two-dimensional materials (paper, photographs, maps, etc.) express the extent either as a linear measure or as a page or item count. (A linear measurement expresses length; a cubic measurement expresses volume, which is length times width times height.)

Linear Measure
When indicating a linear measure, use the terms "linear feet" and "linear inches."

  • If a foot or more, enter the feet and inches to the nearest inch.


10 linear feet


1 linear foot, 5 linear inches
  • If less than one foot, enter the linear inches to the nearest inch.


9 linear inches


1 linear inch
  • If less than one inch, enter decimal fractions of an inch to the nearest .1 inch, but not less than .1 inch.


.5 linear inch


.1 linear inch
  • If less than .1 inch, enter the term "Negligible" or indicate the item or page count.




2 pages


How to Measure
Determine the linear measurement as follows.

  • In general
    Measure the material in the direction a user would look through it - perpendicular to the face of the document.
  • Boxed records
    If the records are in a box, measure them by the way they run in the box. For example: If the records are tri-folded and standing up, the measurement would be up to 12 inches in a letter size box. If the records are unfolded and filed vertically, the measurement would be up to 5 inches in a letter or legal size box.


    If the records completely fill their containers, it is possible to use the container measurements as a convenience to calculate extent for large series. When multiplying container width to determine linear measure, use the width of the box as stated in the Holdings Measurement Type Authority List. For example, for LTA-S and LGA-S boxes, multiply the number of boxes by 5 1/4 inches. If multiplying by the length of the box (for example, for tri-folded paper filed from front to back), use the length as stated in the Holdings Measurement Type Authority List.

  • Cards
    If measuring cards, measure them by the way the cards run in the box.
  • Bound records
    If the records are bound volumes, measure the widths of the spines.
  • Rolled maps, plans, etc.
    If the records are rolled maps, plans, blueprints, or posters, flatten the material and measure the thickness. (An estimate will suffice if the materials are too fragile to be rolled out and flattened.)

Page or Item Count
When indicating a page count, use the term "pages." If necessary, the page count may be estimated. If the archival materials are comprised of various media types, distinguish each type to make the extent measurement as accurate as possible.


Approximately 6,000 pages


15 pages, 4 photographs


267 posters


Three-dimensional Materials
For three-dimensional materials, indicate the number of items and the media type (reels, rolls, cassettes, artifacts, etc.).

The length of film on rolls or reels is entered in Footage or Total Footage.


8 rolls


2 video open reels


Approximately 200 artifacts


3 cassettes

If needed to clarify the amount of archival material, indicate both the intellectual count and the physical count.


100 films on 1,000 film reels


Data Files
For electronic records, indicate the number of data files or type of logical data records. A logical data record is a set of data processed as a unit by a computer system or application independently of its physical environment. Examples of a logical data record include a word processing document, an e-mail message, each row in each table of a relational database, each row in an independent logical file database.


5 data files


40,476 digital image files


Approximately 13,000 e-mails



1 data file and 2 linear inches of paper documentation



34 data files and 34 pages of paper documentation



23 data files and 2 linear feet, 3 linear inches of paper documentation



2 data files, 1 summary statistics file, 11 machine-readable documentation files, and 8 linear inches of paper documentation


Accuracy and Precision
Be as accurate and precise as possible. Do not say "1,000 photographs, 1 linear foot," which implies there are photographs and some other materials, when the actual amount is "1 linear foot comprised of 1,000 photographs."

Say "2,000 maps" instead of "2,000 items."

The extent may be estimated if necessary.

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