Rather than multiplying by 256 colors/dot, I think you should be multiplying by 8 bits/dot (same as 256 colors). Also, 1,800,000 bytes is a MB, not a GB. So it really should look something like this: 300 dot/in * 300 dot/in * 8 bits/dot * 8.5 in * 11 in = 67,320,000 bits per page = 8,415,000 MB