Make a list. Check it twice. Add it thrice.

Santa’s list needs some math.

I have one money hack that will blow your mind rather than blow up your credit card—it’s math. No, not calculus, algebra or geometry, but simple addition and subtraction.

I learned this holiday hack several years ago when I was facing a tight budget. My husband and I were newlyweds with a baby and a fledgling business both sucking money at a terrifying pace from our checking account. The years prior were the same playbook. Assume gifts could cost around $500 and then with shock and dismay learn they were more, a lot more, by double or triple. I would run out of money and go do that rob Peter to pay Paul thing.

So I dusted off a trusty old blank Excel spreadsheet, and I made a list of all the people I would buy gifts for and how much for each. In my head I thought I could spend $100 on loved ones, but very quickly I realized that I ran out of money pretty fast at that rate. So I cut it to $50 where possible. Then I remembered—Christmas cards! I had a baby, so of course we would do one. What’s that? It’s gonna cost $150 with stamps? How about the parties, where I show up with a bottle of wine? Or gifts for my son’s daycare workers and my husband’s coworkers?

Check, check, check.

While I don’t remember the exact total nearly 8 years ago, it was a crazy number that I almost didn’t believe. And remember, that was the number assuming I could even find presents at the halved amounts.

How did my brain get it so wrong? Thinking, “Oh, yeah, Christmas should cost me about 500 bucks.” It’s good old mental accounting gone wrong. Our brains have been studied, and apparently, they just aren’t that good at estimating the sum total of it all.

Think of an Excel file or a paper list with a running total in your purse as your external brain.

Back to my story, I would love to be able to say I did something radical that Christmas. The truth is, I did cut on the margin, but I still spent absolutely way too much money. But it did change things for the following year. First of all, in my system of savings buckets, I have a gift bucket that I contribute to throughout the whole year and includes savings for Christmas. The first thing I did was be honest with myself that it was way more expensive than I had estimated. So I increased my monthly savings into the gift bucket and reduced our weekly discretionary spending to accommodate that.

Then I called off gifts. And was promptly rejected. So I went back to the family regime with a compromise. Can we please draw names? The proposal was accepted.

Ok, so year 2 of the math Christmas thing was a totally different story. First, I had a far more reasonable budget to work with. Second, I had fewer people to budget gift giving for. Third, I found myself continuously resisting the urge to add new “expenses.”

The truth is, the math feels harder these days. Did I change? I don’t think so. Maybe it’s social media. Maybe it’s better marketing. But I want so much more now.

A few years ago I bought into (literally like paid money) the tree design where you wrap so much mesh ribbon and oversized ornaments on the tree that it is impossible to see a shred of green in the tree. Check. Now trends are telling me no ribbon and thousands of small, old-timey classic ornaments. Shoot, I already gave those away to Goodwill! Can I get them back? And then matching family Christmas pajamas. Ugh, how do I resist monogrammed, perfectly Instagrammable matching pajamas? And Christmas cards get fancier and more expensive every year—do I upgrade to the folded card? With glitter? Is life worth living without Santa hot chocolate mugs?

The math just doesn’t work in my favor for all these wonderfully commercial ways to celebrate Christmas, so unless I want to rob Vacation Peter to pay Christmas 2020 Paul (no way) we will have to have a holly jolly Christmas—probably wrapped in a lot of mesh again this year.