TikTok Loves Girl Math—Is It Brilliant or Deranged?

‘Girl Math,’ the latest trend to take TikTok by storm, is basically a clever way to describe the “creative” logic women apply to justify and explain their purchases, especially big-ticket items. Recently, a New Zealand-based radio show Fletch, Vaughan & Hayley thrust the concept into the spotlight with a new segment dedicated entirely to the phenomenon.  

A recent installment—which garnered over 6 million views on TikTok—applied Girl Math to a listener’s indecision about investing in a full set of linen bedding valued at $656. The hosts of the show helped her reason through the splurge. They looked at the number of items included (4 pillows, a top sheet, a bottom sheet and a duvet, so 7), then they assessed that cheaping out on a less luxe set could be costly, too. (“Her partner runs hot, so now you’re sweating through whatever cheap sheets you’re going to buy instead and the mattress protector…which will run you $200 to replace,” one of the hosts explains.)

Finally, the cost-per-use is evaluated: If the listener were to use the sheets 365 days a year and you round the total cost up to $700, she’s getting a good night’s sleep for $1.90/night. Divide that with her partner and you’re down to 95 cents. “It’s basically free!” the hosts proclaim.

But is Girl Math brilliant or offensive? We asked a personal finance expert to weigh in.

About the Expert

Kelly Ann Winget is the founder and CEO of Alternative Wealth Partners, a private equity company based in Texas. She’s also the author of Pitch the Bitch: Grab Your Financial Future by the Bags.

The New Zealand radio segment is pretty clear about the logic of Girl Math, but Tik Tok explainers—like this viral series from user @thebobmarleyy——abound. Some of the more commonly surfaced rules include:

• If you return an item, the refund you receive is basically free money or a profit

• Anything you buy with cash is free

• You’re losing money if you don’t shop at your favorite store when there’s a sale

• If something is less than $5, it’s free

• If you’re shopping and it will cost you $10 more to get free shipping, even if the shipping is $4, you should spend the $10 dollars because it’s a better investment

• Anything in your Venmo account that someone paid you back with is free money

Some of these rules might feel financially problematic—they are—but a quick reminder from Winget: Girl Math is meant to be fun. “Women are taking ownership of the thought process and rationalization of discretionary spending and that’s a good thing,” she says. “The conversation isn’t, ‘Do I pay rent or go to a Taylor Swift concert?’ It’s, ‘I’ve already bought a Taylor Swift concert ticket and this is how I’m rationalizing it in my brain.’”

Humor is one of the core values of Girl Math. But to legitimize the concept for a minute, think of it this way: a creative approach to mental accounting and applying rationale to the way we use our cash.

For example, let’s discuss the found-in-your-Venmo-account rule. “On some level, this concept is the same as a secret account you kept from your spouse,” Winget explains. “Maybe you used the shared family credit card to pay for dinner, but then your pals pay you back for drinks on Venmo. It’s viewed as a separate asset, which is where the ‘free money’ concept comes in.” In other words, it’s your little secret, and as long as it’s not large sums you’re hiding, it’s all in good fun.

Winget also supports Girl Math as a way to free up time for busy women. Think: using it to assess the cost of a Dyson hair dryer. “Yes, they start to break it down by the cost per strand, but the core argument from the listener is that it saves her 30 minutes a day. That’s a huge value and outweighs the dollar amount because of X, Y and Z. It’s also what gets calculated as part of Girl Math,” Winget says.

Finally, Wignet thinks of it as a productive way to consider bigger investments—say, buying a rental property. “If it’s going to cost me $100,000 and my expenses add up to $20,000 per year on insurance and taxes and whatever else, that makes sense,” Winget explains. “But then if I do X, Y and Z, I can earn $50,000 a year renting it out. And that $50,000 becomes $30,000 because $20,000 is going to the extra cost of paying down that $100,000 investment. But after a few years, I’ll have free money, right? Again, that’s pretty much Girl Math.”

If you’re using it to justify purchases that will put you in the hole, that’s a problem,” Winget explains. But she’s clear that Girl Math isn’t likely to be a gateway to bad spending habits. “If that’s the case, you likely already have a lack of self-control when it comes to your cash. Think of it this way, if you are labeled as someone who should never go to Vegas, you should stay away from Girl Math.”

Girl Math is mainly about figuring out how purchases fit into your financial picture. That doesn’t preclude you from having a solid approach to money management, budgeting and debt, but the women who are using Girl Math know that it’s silly, but they’re in on the joke. “It’s about openly rationalizing our spending decisions, which is empowering,” says Winget.