Physical extent
The volume of paper records is determined by cubic foot. Please note that a records center carton (aka Paige box), which measures approximately 10 × 12 × 16 inches, is generally counted as a cubic foot, even though it is slightly larger.
At the collection-level, physical extent should be calculated based on volume of the boxes themselves, not the contents of the boxes. For example, if the last box in the collection is a records center carton and it's only 75% full, this should be counted as 1 cubic foot, not .75 cubic foot. This is because, at the collection-level, we want to account for the physical space occupied on the shelf.
At the series-level, because of the nature of physical arrangement housing not always matching the intellectual order, it may make sense to express the extent based on the materials themselves rather than using the box size to calculate extent. For example, a given series may be housed in three boxes, but in two of those three boxes the series only accounts for a couple folders. In this case, it would be preferable to take a percentage of the box taken up by those folders to calculate extent (ex: 1 cf + .02 cf + .02 cf = "1.04 cubic feet in 3 records center cartons"). Please note that when taking this approach you will not be able to calculate the collection-level extent by adding up each of the series-level extents; you should calculate the collection-level extent based on the volume of all of the boxes in the collection.
Extents of common box types:
| Letter size document box | 0.4 cubic feet |
| Half letter size document box | 0.2 cubic feet |
| Legal size document box | 0.5 cubic feet |
| Half legal size document box | 0.25 cubic feet |
| Records center carton | 1 cubic feet |
FEET vs FOOT
Always use FEET, even for values of 1 or less
(This is an Aspace thing, but please do the same in MARC for the sake of consistency).
Single-folder extent (generally used for small collections/accessions)
0.02 cubic feet is a good average for one folder of materials, could use .01 for a very slim folder and up to .05 for a thick/expanded folder.
Digital extent
Digital extent should ALWAYS be expressed in gigabytes at the highest level of description (collection-level for manuscripts, series-level or record group-level for archives). Counts should be rounded to the nearest two decimal places, and values less than 1 should start with a leading zero (ex: 0.5, not .5).
Digital extent should be recorded in a separate element from the physical extent in the bibliographic record (add a second 300 field), in the Aspace accession record (add a second extent, portion="part"), and in the finding aid (add a second <physdesc>).
Estimating digital extent for media:
If you are describing disks at the point of accession and you are not imaging the disks, calculate the estimated extent in gigabytes based on the maximum capacity of each piece of media:
- 3.5 inch floppy disk (1.44 MB per disk) = 0.01 gigabytes
- 1 3.5 floppy disk = 0.01 gigabytes
- 10 3.5 floppy disks = 0.01 gigabytes
- 25 3.5 floppy disks = 0.02 gigabytes
- 20 3.5 floppy disks = 0.03 gigabytes
- 1 CD (700 MB) = 0.68 gigabytes
- Digital video = 1 gigabyte for every 5 minutes of video. So:
- Mini DV (83 minutes) = 16.6 gigabytes
- DVCAM (124 minutes) = 25.3 gigabytes
- Zip disks usually have the MB on them:
- 100MB = 0.1 gigabytes
- 250MB = 0.24 gigabytes
- 750MB = 0.73 gigabytes
Example digital extent statements for unprocessed/unimaged media:
0.01 gigabytes (1 3.5 inch floppy disk).
4.71 gigabytes (1 zip disk and 1 digital video disc (DVD).
Example of unprocessed electronic media accrual to processed collection (these would be coded as two separate 300s/extents):
2 gigabytes (817 digital files, 10 digital folders).
0.02 gigabytes (2 unprocessed 3.5 inch floppy disks).
Calculating actual extent:
If you know the ACTUAL gigabytes, either because 1) the electronic records were acquired as part of a server-to-server transfer or 2) you have imaged media either during accessioning or processing, provide the digital extent of the records on network storage.
If, during processing, you encountered media that you were unable to image successfully (ie imaging failed or media were determined to be blank), omit those from the digital extent rather than estimating the theoretical digital space they would/could take up. The unimaged media should naturally be included in the physical extent by virtue of taking up space in containers.
Calculate digital extent based on the Use Copies folder once all use files have been extracted from disk images and all "digital detritus" has been removed (system files, etc). Do this by right clicking on the Use Copies folder and selecting Properties. Record the total volume and contents of the Use Copies folder in terms of gigabytes (use the Size count rather than Size On Disk), number of files, and (if applicable) number of folders. Even if you know that some of the files are "unreadable" due to file corruption, lack of rendering software available, etc., record the total volume. If some media were not able to be imaged during processing, do not count these in the digital extent (since we keep the disks they will be represented in the physical extent).
If you have a disk image but have not extracted use files, for instance - a server transfer at the point of accession, use the volume of the disk image(s) as your digital extent.
When adding an unprocessed accrual of electronic records to an existing/processed collection, record the unprocessed volume separately (see example below).
Example digital extent statements for extracted files on network storage:
0.02 gigabytes (39 digital files, 12 digital folders)
7.98 gigabytes (17,826 digital files, 2,361 digital folders)
3.02 gigabytes (digital files on network storage). [unprocessed accession example]
Example of unprocessed server transfer accrual to processed collection (these would be coded as two separate 300s/extents):
2 gigabytes (817 digital files, 10 digital folders).
4.71 gigabytes (unprocessed digital files on network storage).
Example of an unprocessed accession with both e-media and direct transfer digital files:
2 gigabytes (digital files on network storage, 5 3.5 inch floppy disks, and 1 DVD).
For Websites archived using Archive-It
The digital extent for each crawl should be logged in the Archive-It tracking database (N:\Collections\07_Collections_Databases_and_Lists\ArchiveIt_Tracking.accdb). You can find the digital extent in the Archive-It Crawl Report under Crawl Overview. The extent is located under New Data.
Example of digital extent for an archived website:
2.3 gigabytes (1 archived website).