Backup Retention Calculator
Retention is usually chosen by habit and paid for by surprise. The number of copies sets both the bill and how far back a restore can reach, and those two pull in opposite directions.
The calculator
Enter your figures and press Calculate.
Arithmetic on your figures. No retention policy, change rate or storage price is assumed.
How it works
Every line of the result is derived from the numbers in the boxes above and nothing else. The working is printed step by step so you can check it, disagree with it, or redo it on paper.
What it does not do
It supplies no rates, no benchmarks and no view on what a good number looks like — those depend on your situation and belong to you. Nothing is sent anywhere or stored.