Paper Drafting Sizes - ISO 216 series A, B and C

ISO 216 "Writing paper and certain classes of printed matter; Trimmed sizes; A and B series" specifies international standard (ISO) paper sizes, used in most countries in the world today with three series of paper sizes: A, B and C. Series C is primarily used for envelopes.

ISO A Series

The ISO A series of sheet sizes is based on a constant width to length ratio of 1:√2 (rounded to the nearest millimeter). The A0 size is defined as having an area of one square meter (1 m²). Paper weights is expressed in grams per square meter.

Each smaller sheet size is exactly half the area of the previous size.

ISO 216 does not define sizes larger than A0 or B0. With the German standard DIN 476 "Trimmed sizes of paper" the sizes can be expanded by using a factor in front of the size:

• 2A0 is twice the size of A0
• 4A0 is four time the size of A0

Oversized ISO A Sheets

Oversized sheets are used when it is desirable to give extra protection to the drawing sheets by providing a binding or trimming margin.

ISO B Series

The ISO B series are geometric means between the A series and defined to satisfy the requirements of sizes between the A series sizes. For example, B1 is a geometric mean between A1 and A0.

ISO C Series - Envelopes

Series C is primarily used for envelopes. The C series formats are geometric means between the B series format with the same number and the A series format with the same number - C2 is the geometric mean between B2 and A2.

An A4 page will fit into a C4 envelope, A5 will fit into a C5 envelope and so on.

Other Commonly Used Formats

Temperature ^oC
K
^oF

Length m
km
in
ft
yards
miles
naut miles

Area m²
km²
in²
ft²
miles²
acres

Volume m³
liters
in³
ft³
us gal

Weight kg_f
N
lbf

Velocity m/s
km/h
ft/min
ft/s
mph
knots

Pressure Pa
bar
mm H₂O
kg/cm²
psi
inches H₂O

Flow m³/s
m³/h
US gpm
cfm