Every few days there’s a new trend on TikTok — it’s hard to keep up. But one financial trend has tongues wagging more than others, and people not in on the joke are scratching their heads about just what exactly it means.

Girl math took the popular video-sharing platform by storm a few months ago and has been trending ever since.

What is girl math? Whenever we use questionable logic to explain a purchase, that’s girl math.

If you return something, the money you receive back is ‘free money’ according to girl math logic. Buy something for less than $5? It’s practically free, says girl math.

But there’s more to this logic than meets the eye. Girl math is meant to be tongue-in-cheek to help explain the ways men and women alike may justify certain spending habits.

Here’s what to know about the girl math trend.

Where did girl math start?

The viral trend of young women explaining their usually extravagant purchases on the app all started in an unexpected place — a New Zealand-based radio show called Fletch, Vaughan & Hayley.

The hosts work with listeners to justify purchases until they’re “basically free.” In one segment, arguably the most well-known by now, the team got to work justifying one listener’s $5600 splurge on airfare, accommodation, and tickets to four Taylor Swift concerts in Sydney.

@fvhzm Replying to @Sarah Dennis Girl Math- The Eras Tour Edition 🫶 Let us know if you need us to justify your spending 🤪 #girlmath #theerastour #itsbasicallyfree ♬ original sound - FVHZM

The listener saved money by buying tickets for the Sydney shows instead of the European shows, saving four times as much on airfare.

By “girl mathing” the details, the radio hosts were able to justify that the tickets and airfare were essentially free (compared to the European prices).

The idea exploded from there, moving to TikTok, with one user, Daniela Soto, explaining to her followers that “if something is on sale and I don’t buy it, I’m losing money.” Another girl mathism according to Soto: cash isn’t real money, so anything purchased with cash is free.

Soon, TikTok was awash in people explaining away their Taylor Swift Eras Tour ticket purchases or rationalizing Botox injections as an investment, all under the banner of girl math.

@danielasotohealth Girl math makes me feel seen 🥹#greenscreen #girlmath #girlmaths ♬ original sound - daniela | holistic health

Other examples include:

  • Skipping your daily coffee run is actually making money.
  • Any money in your Venmo or PayPal account is free money.
  • Paying for a meal with a friend who pays you back in cash is making money.
  • Returning items for cash is free money.
  • Small purchases, less than $5, are basically free.

Is girl math sexist?

It’s easy to see how the idea of girl math could raise some eyebrows and lead to the assumption that the trend portrays young women in a negative and financially irresponsible light.

However, personal finance experts and girl math-ers around the world say that’s not the case.

“Honestly, girl math is really funny, and I think people are blowing it out of proportion,” 25-year-old content creator Mandy Mitchell told The Guardian.

“They’re flipping the narrative to make it seem like girls are dumb, which is upsetting, because can’t we live and have a funny joke that doesn’t equate to our intelligence? I think that all too frequently when women talk, men do not have the nuance to understand if we’re being ironic.”

Lindsey Stanberry, former executive editor at Fortune magazine, told TODAY.com that she is glad to see young women able to discuss their finances so openly and finds the trend both relatable and funny.

"While I think that the trends definitely started as good fun ... the women who started it are hilarious and it's very funny and very tongue in cheek — it can quickly spiral into being taken as a representation that women don't know how to manage their money, and I don't think that's true," Stanberry said.

Obviously, there are some extreme examples of girl math, like the Taylor Swift tickets, that should not be taken seriously, but as a whole, the trend just highlights something everyone does when it comes to money.

And if nothing else, at least people are being mindful of their expenses. "You could argue that it's not bad math,” Stanberry said. “They're being thoughtful about how they're spending their money."

Additionally, there are examples of “boy math” that insinuate men also approach spending decisions in similar ways.

If a necessity — say a large pack of toilet paper — goes on sale, you have to buy it or you’re losing money. It’s slightly different from girl math, but ultimately shows how our brains justify making different types of purchases.

The TLDR on girl math

As long as you’re not spending beyond your means and accruing debt to make purchases, girl math is harmless.

But if you start overspending and try to justify the expense using any type of logic, that’s when you can get into trouble.

With interest rates higher than they’ve been in a decade, it’s more expensive right now to accrue credit card or loan debt. Sticking to a budget with some wiggle room for non-essentials can help you accommodate pop-up purchases.