Girl Math: The Playful Logic of Justifying Joy

There’s a tongue‑in‑cheek term floating around these days called “girl math.” It’s the art of rationalizing purchases or spending habits that might otherwise be labeled indulgent—or even irresponsible. Little did I know, my mother trained me in this long before the phrase was coined.

After a shopping spree, Mom and I would leave our bags tucked safely in the trunk. Slowly, over time, we’d move the purchases inside. So, when Dad asked if my outfit was new, I could honestly say no—after all, it had technically been “around” for a while.

A dear college friend of mine, Terri Smith‑Kiesenhofer, recently shared her own version of girl math. She and her travel friends each contribute $200 a month into a shared savings account. When vacation time rolls around, all the mutual expenses—meals, Ubers, excursions—come out of that fund. Other than airfare, no one has to split checks or tally receipts. The theory is simple: if you’ve already paid for it, it’s basically free.

Other examples of girl math are equally brilliant:

If you loan someone money and they pay you back, that’s found money.

Spending from a Venmo balance feels like the purchase is “on the house.”

Souvenirs bought in foreign currency don’t count as spending real money.

Buying in‑store instead of online means you’ve “saved” by avoiding shipping.

If you didn’t spend today, you’ve earned splurge money for tomorrow.

Talking yourself out of a purchase is the same as making money.

Returns with store credit? That’s house money, ready to play again.

My personal favorite is the prepaid surprise. Pay for a vacation six months in advance, and when the trip arrives, it feels complimentary. Or buy something during QVC’s Christmas in July, then forget about it until December when a package shows up at your door—a happy little “no‑charge” surprise.

Of course, I’m not suggesting anyone go into debt chasing these playful equations. But who doesn’t love a little splurge now and then? And if you can justify it with girl math, all the better.