O.K.
Take your download speed
Mine = 600kb
Now this is the usually "hidden" bit. To make their connection sound better than the rest, ISPs calcualte bandwith in KiloBits per second, and the rest of the world works in kilobyes per second
To convert from megabits to megabytes:
Number of megabits per second
8
Now take the download size and multiply it by 1000, to convert it to kilobytes
Divide the download size by the download speed, then multiply by 60 to get the number on mins needed for the download.
Example: my connection in 600kb per sec
600/8 = 70 kiloBYTES a sec
download size : 700mb
700*1000 = 700,000 kilobytes
700,000 / 75 = 9333.33
9333.3333 / 60 = 155.55
155 mins so 2 and a half hours
HAVE FUN ALL