I love explaining what “girl math” is to my friends who gamble because they seem to think that I’m the financially irresponsible one. In reality, their hobby costs them more than girl math ever could, and is quite frankly, unattractive.  

The science behind girl math is focused on the change in one’s bank account. Things purchased with money from returns, gift cards, and cash payments can all be thought of as “free” because no money is withdrawn from the bank account. If I purchase a coffee in cash, it’s technically free because my bank account’s balance is unchanged. Similarly, if I receive a refund for an item, technically, I gained money because the number in my bank account went up.