• Facebook
  • Twitter
  • LinkedIn
  • reddit

“If I already have money loaded into my Starbucks app, my Starbucks is free.” “I bought tickets to this concert months ago, so anything I buy at this concert is totally separate.” “If I return a jacket and get $50 back, I made $50.” “It’s Girl Math.” 

You may have heard the phrase Girl Math floating around the internet lately. Coined by many individuals on TikTok, Girl Math refers to specific ways to think about money and how it’s spent, specifically by women and girls. And while this might seem like flawed logic or shady financial thinking, it’s actually just a more modern, Gen-Z-ified way of describing an established economic concept: sunk costs.


Sunk costs refer to any money that has been spent and therefore can’t be recovered. The idea that you make the decision to spend a certain amount of money, and once the money has left your bank account, it’s considered 100% spent and gone. 

Say you’re loading $10 into your Starbucks mobile app on Monday to use on drinks throughout the week. You account for that expense on Monday when the $10 leaves your bank account and transfers to your Starbucks app. Now on Wednesday when you go to get your Starbucks for the day, it feels like it’s free because the price of the drink isn’t coming out of your bank account. You’ve already ‘sunk’ that cost, accounted for it, and there’s no way to get it back. 

Sunk costs can appear in lots of different areas of spending. You sink costs into a concert when you purchase concert tickets months in advance, so anything you buy at the actual event feels like completely separate costs and therefore make the total amount you are spending on that event feel lower. You sink costs when you buy a jacket, only to discover that it’s too small. When you return it and get a refund, it feels like you’ve made money, even though you end up with the same amount of money you started with before you bought the jacket. 

Girl Math and sunk costs are not exclusive to women and girls or ‘frivolous’ purchases like Starbucks or concert tickets. Sunk costs are very relevant in business finances and decision making as well. Sunk costs are a normal part of everyday finances, even though we may not think of them all the time.


The concept of sunk costs can also lead to a potentially problematic way of thinking called the Sunk Cost Fallacy. The Sunk Cost Fallacy refers to the idea that a plan is justified and must be followed through based on the amount of money that has already been sunk into it. You may be tempted to pursue something that is not wise because if you abandon it now, you will lose all the money you’ve already spent. This fallacy comes from a number of physiological factors such as loss aversion and commitment bias, but when it comes to making decisions, it is important to make the smartest and safest decision possible, even if that means taking a monetary loss. 

While it may be fun to joke about Girl Math online, the concept of sunk costs is real and important to understand when it comes to understanding your own financial behavior. 

Ready to save some money? Create a Qube Money account today!