It’s a tale as old as travel. How many undies should you pack? Do you need one for each day? Maybe each night as well, if you’re in a dorm room sitch. Or do you wash on the reg? Wear them inside out? Let your bits go free? It’s a real and true dilemma folks. One that heroes to undie wearers everywhere all-around all-round legend Karina Judd and Jess Evans who set out to resolve using good ole’ maths and science.

The whole thing came about when this meme was posted to a Facebook group they’re both a part of, Meme Queens:

It obviously struck a nerve, and tbh, same, because then another group member posted her own formulaic solution. It calculates the exact number of undies you’d need, based on the varying factors of your trip and your body. Cop the clever formula below:

Using this formula as a starting point, Karina took the idea and really rolled with it, turning it into an Excel spreadsheet to do the hard part for those of us who stopped doing maths after high school.

I saw that [the other group member] had made this post asking for feedback from the scientific community but no peer review was being offered,” explained Karina, “As a scientist, I wanted more from the maths. So I stepped up. Women in STEM (science, technology, engineering, and mathematics) have to lift each other up. The [Excel] calculator is inspired by Jess’ formula but has a number of key differences and improvements.”

YAS ladies, I am here for this.

The spreadsheet takes into account the expected things, like the number of days you’ll be on vacay and how often you’ll be doing the washing. Then it adds the factors of period heaviness (a REAL issue, you never know when she’s gonna leak), that whole about to/have given birth thing, what the weather will be like and any dodgy water with the consequent dunny issue you may face.

Like I said, genius. However, Karina does warn that the formula is still a work in progress and is more like a guideline than an absolute.

The formula behind the calculator isn’t perfect by any stretch, but it does work for most realistic situations. I can’t help you if you input you’re going away for several years with IBS, dodgy water and no intention of doing laundry ever! We’re up to version three already. A future version would include a “packing light” option – although selecting “wash every second day” under laundry will give a similar result.

As for that whole do I need to go bare down there or wear my undies every which way, Karina says the calculator “is designed for normal and fairly realistic undie wear – so none of this inside-out, back-to-front nonsense!

So has Karina used the calculator for any big trips yet?

I haven’t used the calculator for any of my own trips yet [because] it’s still so new, but I do travel frequently and the numbers check out for what I would consider reasonable, balancing necessary vs realistic packing space. Some commenters on the Facebook post have also mentioned it lined up with what they took, which seems like a success.

Have a gander and try it out for yourself right here. Happy packing, may your undies always be clean and fresh.

https://smart.link/5baab15bf819d

Image: Instagram / [@sofiavergara]