B4 – ISO paper sizes B series formats

250 × 353mm | 9.8 × 13.9in

ISO 216 specifies tolerances for the production of B series paper sizes in the same way as for A series paper sizes, the specific details of which are as follows:

  • ±1.5 mm (0.06 in) for dimensions up to 150 mm (5.9 in)
  • ±2 mm (0.08 in) for lengths in the range 150 to 600 mm (5.9 to 23.6 in)
  • ±3 mm (0.12 in) for any dimension above 600 mm (23.6 in)

The B series paper sizes are defined in ISO 216 in the following way.

The B series paper sizes were created in order to provide paper sizes that weren’t covered by the A series, but also use an aspect ratio of 1:root2. B sizes are defined as size B(n) being the geometric mean of size A(n) and size A(n-1). The Geometric Means of 2 numbers being the square root of the product of the two numbers.

This system gives a useful property for enlarging and reducing documents in that the enlargement from A(n) to B(n) is the same as that from B(n) to A(n-1).

As with the A series paper sizes, the standard lengths and widths are rounded to the nearest millimeter.

ISO 216 specifies international standard (ISO) paper sizes used in most countries in the world today, although not in Canada, the United States, Mexico, Colombia, or the Dominican Republic. The standard defines the “A” and “B” series of paper sizes, including A4, the most commonly available paper size worldwide. Two supplementary standards, ISO 217 and ISO 269, define related paper sizes; the ISO 269 “C” series is commonly listed alongside the A and B sizes.

All ISO 216, ISO 217 and ISO 269 paper sizes (except some envelopes) have the same aspect ratio, √2:1, within rounding to millimetres. This ratio has the unique property that when cut or folded in half widthways, the halves also have the same aspect ratio. Each ISO paper size is one half of the area of the next larger size in the same series.

B2+ and B1XL (Also known as B1+) are oversize/uncut B paper sizes. These are not defined by ISO and have come about due to an industry need.

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