ISO 217 explained

The ISO 217:2013 standard defines the RA and SRA paper formats.

Overview

These paper series are untrimmed raw paper. RA stands for "raw format A" and SRA stands for "supplementary raw format A". The RA and SRA formats are slightly larger than the corresponding A series formats. This allows bleed (ink to the edge) on printed material that will be later cut down to size. These paper sheets will after printing and binding be cut to match the A format.

The ISO A0 format has an area of 1.00 m²
The ISO RA0 format has an area of 1.05 m²
The ISO SRA0 format has an area of 1.15 m²

RA	Series formats	SRA	Series formats
RA0	860 × 1220	SRA0	900 × 1280
RA1	610 × 860	SRA1	640 × 900
RA2	430 × 610	SRA2	450 × 640
RA3	305 × 430	SRA3	320 × 450
RA4	215 × 305	SRA4	225 × 320

Tolerances

Paper in the RA and SRA series format is intended to have a

1:\sqrt{2}

aspect ratio but the dimensions of the start format have been rounded to whole centimetres.

For example, the RA0 format has been rounded to 860 mm × 1220 mm from the theoretical dimensions

-	14

\sqrt{1.05} ⋅ 2

m x

	14

\sqrt{1.05} ⋅ 2

m ≈ 861.7mm x 1218.6mm

The resulting real ratios are:

43:61 ≈ 1:1.4186

for RA0, RA2, RA4;

61:86 ≈ 1:1.4098

for RA1, RA3;

45:64 ≈ 1:1.4222

for SRA0, SRA2, SRA4;

32:45=1:1.40625

for SRA1, SRA3.

The sizes of the RA series are also slightly larger than corresponding inch-based US sizes specified in ANSI/ASME Y14.1, e.g. RA4 is roughly equivalent to and ANSI A (alias US Letter) is defined as .

Other ISO paper standards

ISO 216:1975, defines two series of paper sizes: A and B
ISO 269:1985, defines a C series for envelopes

External links

International standard paper sizes: ISO 216 details and rationale
ISO 216 at iso.org
ISO 217 at iso.org
ISO 269 at iso.org