Calculating Savings at Drug Stores

It gets a little tricky calculating your savings at drug stores when you begin to factor in ECB, +Up rewards, and Register Rewards. Whether your drug store of choice is CVS, Rite Aid or Walgreens here's how I keep track of my savings.

Take CVS (can you tell it's my favorite drug store?) for example. Here is one of my most recent transactions.

It'll say on the receipt the sale price with the amount saved on the right. So the original price is $22.99. After coupons I paid $6.99 and received $4 ECB. So my actual OOP is $2.99.

Original price - Price Paid = $20 Saved

Savings / Original Price = 0.87

Move decimal over two spaces to the right = 87% Savings

I like to calculate ECB rewards into the amount saved in the same purchase I received it. When I use my ECB I simply treat it as if I were paying cash so that I don't count it twice which would make my calculations inaccurate. 

I know some people like to calculate their savings when the ECB are used, but that just confuses me. But I confuse easily.