# Glacier Math

Want to figure out how much it will cost to retrieve a backup from Amazon's new Glacier service? So simple:

Next we subtract your free allowance from the peak hourly retrieval for the month. To determine the amount of data you get for free, we look at the amount of data retrieved during your peak day and calculate the percentage of data that was retrieved during your peak hour. We then multiply that percentage by your free daily allowance. In this example, you retrieved 24 gigabytes during the day and 1 gigabyte at the peak hour, which is 1/24 or ~4% of your data during your peak hour. We multiply 4% by your daily free allowance, which is 20.5 gigabytes each day. This equals 0.82 gigabytes. We then subtract your free allowance from your peak usage to determine your billable peak.

If that's not clear, the FAQ references the pricing guide. If that's not clear, the pricing guide references the FAQ. So there it is.

Here's my simple math:

The maximum rate for up to 10TB is $0.12 per GB. Can I just pay that and *not* worry about calculating it?

If I did, my 6TB would cost me $720 to retrieve. It's not a *bad* price but it's double the price of buying two 3TB blank disks. I'll stick with my system for now.

Note: My intention would be to push data to Glacier in preparation for disaster recovery and not to retrieve single directories or files.