We don't pay that much attention to the wide variety of paper sizes out there nowadays, unless of course you're affiliated with the printing industry. But most of us regular folks see paper sizes as legal size or letter size. If ever we need a sheet of paper that is a lot larger we usually just tell the clerk at the store to get something a lot bigger.
As you might expect, there are different sizes of paper all over the world. Different people use different comparable standards. However, today, there is only an international standard that is in use in many countries today. Other than the international ISO standard sizes, there is also a North American Standard in use in the US and other territories today.
North American Paper Standard Sizes
The standard sizes of paper used in the US, Mexico, and Canada coincide with traditional sizes. The terms ledger size, tabloid, legal, and letter size often rings a bell. The letter size is 8.5 x 11 inches or 216 mm x 279 mm. Legal size paper is 8.5 x 14 inches or 216 mm x 356 mm.
Other paper sizes used in the said countries include tabloid, ledger, and junior legal. Tabloid size paper is 11 x 17 inches or 279 mm x 432 mm. Ledger sized paper is 17 x 11 inches or 432 mm x 279 mm. Junior legal size paper is 8.0 x 5.0 inches or 203 mm x 127 mm.
Other countries like Chile and the Philippines use the same standard sizes with a few minor changes. For instance, the legal size paper in the Philippines is 8.5 x 13 inches. Take note that every government or institution can use a combination of size standards when preparing materials for print. For example, Mexico may have adopted the ISO standard but the US standard is still widely used.
ISO and Other Standards
Remember that there have been many standards used in determining the different sizes of paper. Although the ISO standard rose to popularity, other countries can still decide on which standard they want to use. The ISO standard includes the A4 size paper and all of its other related sizes as well.
It shouldn't come as a surprise to find some people who still use the traditional inch based standards. When you hear of "royal paper" or "royal octavo", you can be sure that they are talking about units of this standard paper size. Other units or sizes in this standard include grand eagle, atlas, emperor, antiquarian, demy, and elephant among many others.
To make the job easier, you may want to use the ISO standard as a focal point to compare all other standard sizes. That way you would have a scaled idea on how large a certain paper size is compared to the ISO standard.