Question 1

Bleed

Accepted Answer

is a critical concept in print design that is inextricably linked to paper size. Because industrial cutting machines (guillotines) have a slight margin of error (usually 1 mm to 2 mm), printing an image exactly to the trim edge risks leaving a thin, unintended white line along the border of the paper. To prevent this, designers extend the artwork beyond the trim size by a standard amount—usually 3 mm (or 0.125 inches in the US). This extra area is the bleed. Therefore, to produce a final A4 document (210 × 297 mm) with edge-to-edge color, the designer must create a digital canvas that is 216 mm × 303 mm (adding 3 mm to all four sides).

Question 2

Basis Weight

Accepted Answer

and GSM measure the thickness and density of the paper, which often dictates which paper sizes are appropriate for a given project. GSM stands for Grams per Square Meter. Because the ISO system is based on an A0 sheet being exactly one square meter, a paper rated at 80 GSM means that a single A0 sheet of that paper weighs exactly 80 grams. Since A4 is one-sixteenth the area of A0, a single sheet of 80 GSM A4 paper weighs exactly 5 grams (80 / 16). In North America, the system is much more confusing; Basis Weight is measured in pounds (lbs) and refers to the weight of 500 sheets (a ream) of the paper in its basic, uncut manufacturing size, which varies depending on the type of paper (e.g., Bond paper has a different basic size than Cover stock).

Question 3

What is the exact difference between US Letter and A4 paper?

Accepted Answer

US Letter measures 8.5 by 11 inches, which translates to 215.9 mm wide and 279.4 mm high. A4 paper is part of the international ISO 216 standard and measures 210 mm wide and 297 mm high (approximately 8.27 by 11.69 inches). Therefore, A4 is slightly narrower (by about 6 millimeters) and noticeably taller (by about 18 millimeters) than US Letter. This difference means documents formatted tightly for one size will often experience clipping or margin issues when printed on the other without adjustment.

Question 4

How do I calculate the dimensions of any A-series paper without looking it up?

Accepted Answer

Because the A-series uses a consistent $1:\sqrt{2}$ aspect ratio, each smaller size is exactly half the area of the previous size. To find the next size down, you take the dimensions of your current sheet (e.g., A3 is 297 mm × 420 mm), divide the larger number by two (420 / 2 = 210), and keep the smaller number as is. The new dimensions are 210 mm × 297 mm, which is A4. If dividing results in a decimal, you always round down to the nearest whole millimeter according to ISO standards.

Question 5

Why is US Legal paper 14 inches long?

Accepted Answer

US Legal paper measures 8.5 by 14 inches. The origin of the 14-inch length is historical, dating back to the days of manual document drafting by lawyers. Lawyers needed extra space at the bottom of standard contracts to add signatures, stamps, and brief handwritten addendums without requiring a second sheet of paper, which could easily become separated and cause legal disputes over contract integrity. The 14-inch length provided this necessary buffer while maintaining the standard 8.5-inch width to fit into standard typewriter carriages.

Question 6

What size is a standard business card?

Accepted Answer

Business card sizes are not governed by ISO 216 and vary heavily by region. In the United States and Canada, the standard business card is 3.5 × 2 inches (88.9 × 50.8 mm). In Western Europe, the standard is slightly different, typically aligning with credit card dimensions at 85 × 55 mm. In Japan, the standard "Meishi" size is 91 × 55 mm. When designing business cards for international networking, you must adhere to the local standard, as a US business card will often rattle around loosely in a European cardholder, and a Japanese card will simply not fit into a US wallet slot.

Question 7

How does paper weight (GSM) relate to paper size?

Accepted Answer

GSM stands for Grams per Square Meter. It is a measurement of the paper's density and thickness based on the A0 paper size, which has an area of exactly 1 square meter. If a paper is rated at 100 GSM, a single A0 sheet of that paper weighs exactly 100 grams. Because an A4 sheet is one-sixteenth of an A0 sheet, a single piece of 100 GSM A4 paper weighs exactly 6.25 grams (100 divided by 16). This mathematical relationship allows commercial printers to calculate shipping weights for massive print runs with perfect accuracy.

Question 8

What are SRA paper sizes used for?

Accepted Answer

SRA stands for Supplementary Raw format A. Commercial printers cannot print edge-to-edge (full bleed) directly onto an A4 sheet because the printing press requires a mechanical grip margin to pull the paper through the rollers, and the design requires extra bleed area to allow for trimming. SRA sizes are slightly larger than standard A sizes (e.g., SRA3 is 320 × 450 mm, whereas A3 is 297 × 420 mm). Printers print the artwork onto the oversized SRA sheet and then use a guillotine to trim the excess paper away, leaving a perfectly sized A-series document with color extending flawlessly to the edges.

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