How can you know which is the "current dollar value" of a dollar value from another decade? Is there a mathematical ecuation or some method, which allows you to have the "current dollar value" of an amount dollar from other year, let's say, decades ago? For example, it's said that the Marshall Plan where United States gave 13 billions dollars to Europe is equivalent to $130 billion in current dollar value as of June 2016.
There are quite a few websites which will do a point-to-point calculation for you, if all you want is the comparison of the CPI.  For example, https://www.measuringworth.com/uscompare/

Saying how much a dollar was "worth" at a past point, however, is not a very precise question unless it's made more specific.  The price of computers, for example, have fallen even as they have become more powerful -- and even as the price level has risen.  It's simply not accurate to say that a five-hundred-sixty-three dollar computer today (of which there are many choices) would have cost only $1 in 1774!

I recommend this essay for a lot more detail on the matter.