FILE
SIZE is calculated
by multiplying the surface area of a document (height x width) to be scanned
by the bit depth and the dpi^{2}. Because image file size is represented
in bytes, which are made up of 8 bits, divide this figure by 8.

Formula
1 for File Size File
Size = (height x width x bit depth x dpi^{2}) / 8

If
the pixel dimensions are given, multiply them by each other and the bit
depth to determine the number of bits in an image file. For instance,
if a 24-bit image is captured with a digital camera with pixel dimensions
of 2,048 x 3,072, then the file size equals (2048 x 3072 x 24)/8, or 18,874,368
bytes.

Formula
2 for File Size File
Size = (pixel
dimensions x bit depth) / 8

File
size naming convention: Because digital images often result in very
large files, the number of bytes is usually represented in increments
of 2^{10} (1,024) or more: