The accepted method of referencing blackjack counting system variation is through a parameter known as true count. True count is dependent upon number of cards remaining to be dealt and the system's running count. Running count is simply the counting system's measure of imbalance between two or more groups of cards.
let CR = cards remaining
let RC = running count
let TC = true count
In general: TC = 52 * RC / CR
Once TC has been computed it is used to determine best playing strategy
Below is a more pleasant alternative to having to compute true count. The example shows when to take generic insurance using HiLo counting system for 1 to 8 decks. Generic insurance means specific composition of cards in player's hand is ignored in determining decision. The method is exact only if the Pen parameter is known exactly but estimating it is not complicated. TC method is certainly not exact either.
Method could be used for decisions other than insurance.
Pen = (cards seen) / (52 * decks), RC = HiLo running count
Buy insurance when (Pen, RC) point is above plot for given number of decks
