Physical description (300)
“cm” And “mm.” were abbreviations in AACR; in RDA, they are considered symbols and therefore have no period at the end (i.e., “cm” and “mm”).
Add a period to the end of the 300 field if a 490 is being recorded.
For a multipart monograph that is not yet complete, record volumes in 300 $a. Do not leave leading spaces. Do not supply the latest volume received in angle brackets.
Resources with numbered pages, leaves, or columns
For a resource consisting of a single volume, record the extent in terms of pages, leaves, or columns according to the type of sequence used in the resource. Apply the following general guidelines if the pages, leaves, or columns are numbered, ignoring short unnumbered sequences that are judged to be insignificant:
a) If the volume is paginated (i.e., if there are page numbers on both sides of the leaves), record the number of pages.
300 __ $a 327 pages
b) If the volume is foliated (i.e., if there are leaf numbers on only one side of the leaves), record the number of leaves.
300 __ $a 321 leaves
c) If the volume consists of pages with more than one column to a page and is numbered in columns, record the number of columns.
300 __ $a 381 columns
d) If the volume consists of sequences of numbered leaves and pages, or numbered pages and numbered columns, or numbered leaves and numbered columns, record each sequence if there are three sequences or fewer. If there a four or more sequences, record 1 volume (various pagings):
300 __ $a xvii, 323 pages
300 __ $a 27 pages, 300 leaves
300 __ $a 1 volume (various pagings)
e) If the resource has complicated or irregular paging, etc., record 1 volume (various pagings):
300 __ $a 1 volume (various pagings)
f) Record pages, etc., that are lettered inclusively in the form, e.g.:
300 __ $a A–K pages
300 __ $a a–d leaves
300 __ $a A-Z pages
Resources with unnumbered pages, leaves, or columns
If the resource consists entirely of unnumbered pages, leaves, or columns, apply the following:
a) if there appear to be 50 or fewer pages or 25 or fewer leaves, count the pages* and/or leaves and record, e.g.: 24 unnumbered pages
b) if there appear to be more than 50 pages or 25 leaves, do not bother to to count the pages. Instead record: 1 volume (unpaged)
Resources with numbered and unnumbered pages, leaves, or columns
If the resource consists of both numbered and unnumbered sequences of pages, leaves, or columns, disregard the unnumbered sequences, unless:
a) an unnumbered sequence constitutes a substantial part of the resource
b) an unnumbered sequence includes pages, etc., that are referred to in a note.
300 __ $a 33 leaves, 31 unnumbered leaves
300 __ $a 8 unnumbered pages, 155 pages (Here you are including the unnumbered sequence because a bibliography referred to in a note appears on 6th preliminary page.)
As in AACR2, if the form of numbering within a sequence changes (e.g., from roman to arabic numerals), ignore the numbering of the first part of the sequence:
Pages numbered: i–xii, 13–176
300 __ $a 176 pages
In some cases, the numbering on the last page, leaf, or column of a sequence does not represent the total number in that sequence. When this occurs, do not correct it unless it gives a completely false impression of the extent of the resource (e.g., when only alternate pages are numbered or when the number on the last page, leaf, or column of the sequence is misprinted).
When correcting misleading numbering, record the numbering as it appears on the last page or leaf followed by that is and the correct number.
300 __ $a 48, that is, 96 pages
300 __ $a 329, that is, 392 pages
Pages, Etc., Numbered as Part of a Larger Sequence
If the pages, etc., are numbered as part of a larger sequence (e.g., as part of the continuous paging for a multivolume resource), record the first and last numbers of the pages, etc., preceded by the appropriate term:
300 __ $a pages 713–797
Leaves or Pages of Plates
If the leaves or pages of plates in a resource are not included in the numbering for a sequence or sequences of pages or leaves of text, etc., record the number of leaves or pages of plates at the end of the sequence or sequences of pagination, etc. Record the number of leaves or pages of plates after the pagination, etc., whether the plates are found together or distributed throughout the resource:
300 __ $a 246 pages, 32 pages of plates
300 __ $a x, 32, 73 pages, 1 leaf of plates
If the resource contains both leaves and pages of plates, record the number in terms of whichever is predominant:
300 __ $a 323 pages, 19 unnumbered pages of plates
Resource contains 16 pages and 3 leaves of plates
If leaves are folded, record that they are folded:
300 __ $a 122 folded leaves
300 __ $a 230 pages, 25 leaves of plates (some folded)
300 __ $a 25 folded leaves of plates
Duplicated Paging, Etc.
If the paging is duplicated (e.g., in some books with parallel texts), record both pagings and make an explanatory note
300 __ $a xii, 35, 35 pages …
500 __ $a Opposite pages have duplicate numbering.
300 __ $a xi, EN185, FR189 pages …
500 __ $a English to French terms followed by French to English terms separately paged.
(EN and FR appear as part of the numbering on the resource)
Pages Numbered in Opposite Directions
If the resource has groups of pages numbered in opposite directions (e.g., in some books with texts in two languages), record all the pagings. Record the pagings of the various groups in order, starting from the title page selected for the description: 
300 __ $a iv, 127, 135, vii pages
Text is in English and French on inverted pages; English title page selected
300 __ $a ix, 155, 126, x pages
Text is in English and Hebrew; English title page selected
Record the extent of a resource consisting of a single sheet as 1 sheet: 
300 __ $a 1 sheet
If the sheet is designed to be read in pages when folded, record the extent as 1 folded sheet followed by the number of pages laid out on the sheet, in parentheses.
300 __ $a 1 folded sheet (8 pages)
If the resource contains illustrative content, record illustration or illustrations and/or map or maps, as appropriate (in that order, separated by comma-space). Tables containing only words and/or numbers are not considered as illustrative content. Disregard illustrated title pages, etc., and minor illustrations.
If the content of the resource is in colors other than black and white or shades of grey, record the presence of color using an appropriate term. Disregard colored matter outside the actual content of the resource (e.g., the border of a map):
300 __ $a … : $b color illustrations ;
300 __ $a … : $b illustrations (some color) ;
300 __ $a … : $b illustrations (chiefly color) ;
300 __ $a … : $b color illustrations, maps ;
300 __ $a … : $b color illustrations, color maps ;
300 __ $a … : $b illustrations (some color), maps (some color) ;
300 __ $a … : $b illustrations (chiefly color), maps ;
If the resource consists of only illustrations (with or without captions and excluding bibliographic data, etc.) or chiefly illustrations, make a 500 note (in addition to the 300 $b statement):
500 __ All illustrations.
500 __ Chiefly illustrations.
and add a 336 for the illustrative content (see below).
Record the height of the volume. If the volume measures less than 10 centimeters, record the height in millimeters and use the metric symbol mm:.
300 __ $a … : $b … ; $c 22 cm
300 __ $a … : $b … ; $c 95 mm
If the width of the volume is either less than half the height or greater than the height, record the height × width.
300 __ $a … : $b … ; $c 20 × 8 cm
300 __ $a … : $b … ; $c 20 × 32 cm
If the carriers are of the same type but differ in size, record the dimensions of the smallest or smaller and the largest or larger size.
300 __ $a … : $b … ; $c 24–28 cm
Dimensions of the smallest and largest volumes in a resource consisting of 6 volumes of differing height.
Record the height × width of the sheet, excluding any frame or mount.
300 __ $a … : $b … ; $c 28 × 22 cm
Dimensions of a sheet of text.
If the sheet is designed to be read in pages when folded, record only the height of the sheet when folded.
For other folded sheets, record the height × width when extended followed by the height × width when folded:
300 __ $a … : $b … ; $c 48 × 30 cm folded to 24 × 15 cm
300 Accompanying material (300 $e)
In records formulated according to ISBD principles, subfield $e follows a "plus sign" (+) and contains all remaining data in the field.
See more ISBD punctuation examples for 300 field here
 Adapted from 220.127.116.11 and 18.104.22.168
* When counting pages or leaves in a volume with fewer than 50 pages, count every page/leaf inside the covers (including t.p., t.p. verso, advertising pages, etc.); exclude only the four pages of the cover in your count. If the cover material is of the same paper stock as the rest of the pages, include the four pages of the cover in your page count.
 22.214.171.124, including local option decision
 Adapted from 7.15 and 126.96.36.199 and LC-PCC PS 188.8.131.52
 LC practice is to generally record all illustrative content as “illustrations.” UHM prelim catalogers will record illustrations and maps when appropriate. UHM original catalogers may add other RDA-approved terms (charts, coats of arms, facsimiles, forms, genealogical tables, graphs, illuminations, music, photographs, plans, portraits, samples) at the cataloger’s discretion.
 RDA “carrier types” you will encounter in published textual monograph cataloging are “volume(s)” and “sheet(s)”