Guidance: 
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.
Twodimensional Materials
For twodimensional 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.
 If less than one foot, enter the linear inches to the nearest inch.
 If less than one inch, enter decimal fractions of an inch to the nearest .1 inch, but not less than .1 inch.
 If less than .1 inch, enter the term "Negligible" or indicate the item or page count.
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 trifolded 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 LTAS and LGAS boxes, multiply the number of boxes by 5 1/4 inches. If multiplying by the length of the box (for example, for trifolded 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.
Threedimensional Materials
For threedimensional 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.
If needed to clarify the amount of archival material, indicate both the intellectual count and the physical count.
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 email message, each row in each table of a relational database, each row in an independent logical file database.
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.
