文档大小能衡量一个计算机文档的大小。通常情况下以带前缀的字节数表示。文档实际所占磁盘空间取决于文档系统。文档系统的最大文档大小取决于保留存储尺寸信息的位数量，及文档系统的总大小。例如，在FAT32文档系统中，单个文档的大小不能超过4 GiB。 一些常见的文档大小单位是：

File size measures the size of a computer file. Typically it is measured in bytes or bits. The actual amount of disk space consumed by the file depends on the file system. The maximum file size a file system supports depends on the number of bits reserved to store size information and the total size of the file system.