Paper Sizes

Just how big is A2 paper? Do I need a C5 envelope or a C6? What are the standard poster sizes?
The answer to all these questions (and more!) are on this page.

We'll start with a helpful diagram:

ISO Sizes - Trimmed Stock

'A' Range:
The 'A' Range is the finished trimmed size of paper used in printing and related industries.
A7 105mm x 74mm
A6 148mm x 105mm
A5 210mm x 148mm 
A4 297mm x 210mm
A3 420mm x 297mm
A2 594mm x 420mm
A1 841mm x 594mm
A0 1189mm x 841mm

'B' Range:
The 'B' range covers a need for special applications, such as oversize documents and posters.

B7 125mm x 88mm
B6 176mm x 125mm
B5 250mm x 176mm
B4 353mm x 250mm
B3 500mm x 353mm
B2 707mm x 500mm
B1 1000mm x 707mm
B0 1414mm x 1000mm
'C' Range - Envelope Sizes:
Connected to both envelopes and folders, the 'C' range allows 'A' sized items to be inserted.

C8 81mm x 57mm 
C7 114mm x 81mm 
C6 162mm x 114mm
C5 229mm x 162mm
C4 324mm x 229mm
American Quarto: 
American Quarto is normally used by USA based companies and is generally stated in inches.

11" x 8.5" (279mm x 216mm)
ISO Sizes - Untrimmed Stock
SRA Sheet Sizes:
Known as the supplementary range, this sheet size offers greater flexibility in allowing for bleed, machine handling and finishing.

SRA6 160mm x 112mm
SRA5 225mm x 160mm
SRA4 320mm x 225mm
SRA3 450mm x 320mm
SRA2 640mm x 450mm
SRA1 900mm x 640mm
SRA0 1280mm x 900mm

RA Sheet Sizes:
The 'RA' range allows for a 5% waste when finally trimmed. This range is not widely stocked due to the limitations in application.
RA6 152mm x 107mm
RA5 215mm x 152mm
RA4 305mm x 215mm
RA3 430mm x 305mm
RA2 610mm x 430mm
RA1 860mm x 610mm
RA0 1220mm x 860mm
Classic Series:

Large Post 419mm x 533mm
Demy 444mm x 572mm
Medium 457mm x 584mm
Royal 508mm x 635mm
Double Crown 508mm x 762mm