A page can tell you that inflation erodes what a saving is worth, or it can take the amount you actually hold, the period you have held it, and the rate you are earning, and work out what that comes to once inflation is taken into account. The second kind of answer is what a calculator gives you: figures go in, either your own or ones drawn from a published series, and the working runs in front of you.

What that changes for you

Seeing each step means you can follow it against your own numbers. A projection that moved between two publication dates, a yield curve that stayed inverted for some stretch, a balance that lost ground to inflation: each of these is a calculation built from labelled inputs.

Where the figures come from, and what they cannot promise

Every figure a calculator uses is drawn from a named public source and carries the date it applies to, so the arithmetic can be checked against the original record. That does not guarantee the answer is the one you were expecting: a calculator built from published data can still return a wrong or misleading figure if an input is mistyped, a series has moved on, or a rate has since been revised. Anything typed into one of these tools stays in the browser it was typed into; it is not sent to or stored anywhere by this site. The method behind the figures, and what happens when one is disputed or out of date, is set out on How This Site Handles Figures.