Everybody who has ever held a job, especially in an office, is familiar with the 3 most common sizes of paper – letter, legal, and tabloid. You may have also heard some other terms applied to sizes of paper and wondered what they mean. First, though, some background on papers sizes.
Paper size throughout many parts of the world is guided by an international standard known as the ISO 216 standard. It is based on each size being half of the size of the previous one, when folded parallel to the shorter lengths. This idea was originally proposed by the German scientist Georg Christoph Lichtenberg in 1786, and most of the world has never really stopped using it. The U.S., however, is an exception. (See below.)
This ISO 216 system allows for a variety of useful applications, such as the enlarging and reducing of images without any cutoff or margins, or folding the sheets to make a booklet of the next size down. The most common ISO paper size is the “A” series. It applies to paper as small as A10 (1” x 1.5”) and as large as 4A0 (67” x 94”). For business use, A4 (8.26″ by 11.69″) and A3 (11.7” x 16.5”) are the most used sizes.
The Few Exceptions
A few countries have their own paper size standards. In the U.S., the two most common paper sizes, named “letter” and “legal”. They are similar to A4 and A3, but are not exactly the same.
Our “letter” sized paper (8.5” x 11”) is a bit wider and a bit shorter than A4. Our “legal” size (8.5” x 14”) paper is just a longer version of our letter paper. Ans just to confuse things, our “Tabloid” size paper (11” x 17”) is a bit narrower and longer than its A3 counterpart.
Why the differences? It’s not clear. It has nothing to do with the metric system, as some might expect. It is believed that the difference came about during the days of manual paper making and the personal preferences of the papermakers. But sadly, the full story has been lost to time.
The C series was established to define the sizes of envelopes that may be used in conjunction with the A and B series paper sizes. The C series is defined by the ISO 269 International Standard for paper sizes. The size of C series envelopes is directly related to A series papers.
The most common envelopes for business use are the C4, C5, C6 and DL sizes. Most people consider a DL size envelope a “letter envelope” because it fits “letter” and A4 and size paper folded into thirds. A C6 envelope is designed to fit letter/A4 paper folded into quarters. A C5 envelope is designed to fit letter/A4 paper folded in half, while a C4 envelope is designed to fit unfolded letter and A4 paper.
If you are interested, there are many other regional ISO “extensions” (German DIN standard, Swedish SIS standard, Soviet GOST standard, etc.) and nation-based standards to explore.