Let’s say you have a 600dpi printer a one square inch image will be 360,000 pixels, each pixel will contain 24 bits of information so we have at a minimum 8,640,000bits or 1,080,000 bytes of information without the printer instructions.
So a B1 page (nom 27x40 inches) would be 27x40x1080000 = 1,166,400,000 bytes or 1.166 Gb
Depending on your printer type the multiplier for the printer instructions will vary, postscript printers will typically be smaller than GDI / EMF printers as they can handle the vector data and images directly whereas other printers need the computer to do the processing.