said by roomie :
None of the calculators I've foudn are useful in telling me what max speed I need to keep in order to use only 50 GB per month total.
That is a simple calculation.
First convert 50 GB (gigabytes) into 50 gb (gigabits) multiply by 8
You have 400 gb (400,000,000,000) to use per month.
Connect speed is specified in bits per second so you need to determine how many seconds are in a month: 30d x 24h x 60m x 60s
Assuming a 30 day month there are a 2,592,000 seconds per month. If you want to be more conservative use 31 days for a month.
Dividing your cap by seconds per month yields 154.3 kbps.
That is the total for the connection, you then need to figure out how to divide it up among all the users.
50 GB sounds like a lot but not when you think about it on a sustained basis like streaming or game play.