While the exact amount of text data in a kilobyte (KB) or megabyte (MB) can vary depending on the nature of a document, a kilobyte can hold about half of a page of text, while a megabyte holds about 500 pages of text. Text in a digital file is converted to binary data that indicates letters and numbers through expressions of ones and zeros. Larger files hold more of this data, which in turn is the equivalent of more typed information.
Binary And Bits
Most modern computers are binary systems and work with bits of data. A bit is the most basic unit of information, which can have two states: usually specified as a 0 or 1. Long strings of these bits can represent most types of information including text, pictures and music. Pure binary information, however, is of little use to people who have not learned to read and write in binary. The binary number 11000101110, for example, is equivalent to 1582.
Grouping Bits into Bytes
To help make data more accessible and simplified, groups of bits are joined into bytes; one byte is comprised of 8 bits. A set of 8 bits was chosen because this provides 256 total possibilities, which is sufficient for specifying letters, numbers, spaces, punctuation and other extended characters. This very sentence, for example is composed of 125 bytes because there are 125 letters, digits, spaces and punctuation marks. Keep in mind that this only represents pure text; some word processing programs include other sorts of formatting data, and therefore the file sizes become greater than just the number of characters in the file.
Amounts of Text
A kilobyte is 1,024 bytes, often rounded to 1,000 for simplicity; while a megabyte is 1,048,576 bytes, or around 1 million. It is estimated that a kilobyte can accommodate about one-half of a typewritten page. Therefore, one full page requires about 2 KB. The following chart illustrates the number of bytes in common terms such as kilobyte and megabyte and how much text each can store.
| Name | Number of Bytes | Amount of Text |
| Kilobyte (KB) | 210 or 1,024 | 1/2 page |
| Megabyte (MB) | 220 or 1,048,576 | 500 pages or 1 thick book |
| Gigabyte (GB) | 230 or 1,073,741,824 | 500,000 pages or 1,000 thick books |
| Terabyte (TB) | 240 or 1,099,511,627,776 | 1 million thick books |
| Petabyte | 250 or 1,125,899,906,842,624 | 180 Libraries of Congress |
| Exabyte | 260 or 1,152,921,504,606,846,976 | 180 thousand Libraries of Congress |
| Zettabyte | 270 or 1,180,591,620,717,411,303,424 | 180 million Libraries of Congress |
| Yottabyte | 280 or 1,208,925,819,614,629,174,706,176 | 180 billion Libraries of Congress |
Library of Congress
The Library of Congress in Washington D.C. is said to be the world's largest library with over 28 million volumes. Numbers listed in the chart above are based on the assumption that the average book has 200 pages. This means that about 28 TB of storage would be required to save a digital backup of the entire Library of Congress.
Portable Media Storage
Most Compact Discs (CDs) hold approximately 750 MB, which is roughly equivalent to 375,000 pages of text. Digital Versatile Discs (DVDs) can store 4.7 GB or 2.3 million pages. Blu-Ray discs, can hold 27 GB or 13.5 million pages, which is roughly equivalent to the text contained in 67,500 books. Devices like eReaders and tablet computers often have many gigabytes of storage, making them ideal for carrying thousands of books around.