How to Calculate grayscale image sizes ?

grayscale images use the same 8 bit depth for the dot representation, but the difference to a color image is the bit depth is use to represent a level of gray instead of colours.

By saving images in grayscale can reproduce a image similar to photo mode you find in the photocopiers. The major problem with this type of files are the file sizes. Also the compression techniques used on the black and white images cannot be used with the grayscale images.

The gray scale images are 8 times bigger than the black and white images before compression. This will make the raw grayscale file to be of approximately 4 MB.