Backpacking Insect Repellent Trip Supply Calculator

Nothing looks better on a map than a backpacking trip, until it’s dark out, there are mosquitoes everywhere, and that long hill gets its own share of deer flies up your neck. So will you be carrying repellent? Yes. But then: How much? And how do you avoid making your pack into a chemistry set?

Letting you skip all that math (and guessing about how much buffer/when to reapply), this calculator take various inputs like group size, exposure hours, and product type to do the rest for you. Because the inputs represent real-world events: Trail hours capture the time spent moving through buggy zones, while camp hours reflect slower-paced activities like filtering water or cooking dinner (when bugs is in full force). Clothing choices affect exposed skin area, which is why youth input uses about two-thirds the adult amount (smaller bodies require fewer ounces). Adjustments for sweat and more insects increase totals due to evening swarm events or wet clothing (like sweaty sleeves that force reapplication every few minutes). The type of product also affects results, as lotion tends to spread more precisely than aerosol; and wipes has a bit of package weight to consider.

How to Pack the Right Amount of Bug Spray

Many people make the error of assuming that however long it says on the label is how much they’ll actualy have. That’s not true. Real life includes wind, shared bottles, and the possibility that your shirt might get soaked through. So there’s a reserve margin added to the calculator. It adjusts based off the amount you currently have and container sizes you want to use so that if you’re trying to decide between taking another small bottle, you can figure out if that will still put you over capacity or if you’ll be fine with what’s left in side pocket.

The result is a projected pack weight (which is important on longer trips where ounces count), number of containers, and overall volume of repellent you should of carry. In real life, things don’t quite go according to the clean models. One day it might be long sleeves and the next its shorts and no shirt due to an unexpected weather change. The person with the group who carries his own bottle will end up consuming as much or more then two others sharing a bottle. And nobody predicted those biting flies filling lake basin until you showed up.

But the thing about the calculator is that it provide you with a starting point that assumes some loss for “normal” and has some buffer on top so that instead of starting at the minimum, you start at a realistic place. What’s the best trick? Run the numbers as part of creating your gear list. Then run the numbers again at the end of that day one night out.

What is the biggest driver for using more than planned? It is camp time. The result gives you a sense for if your strategy is conservative or generous with that day’s ration. One such check will turn a fuzzy intuition of “this should be enough” into a concrete decision. You can then stand behind that decision when those bugs arrives exactly when expected.