Compost Bucket Volume Calculator for Camping

But what most RVers come to understand is that composting has little to do with managing waste and much more to do with how much space it takes up.

The compost bins is five gallons because that’s the size of paint buckets at the hardware store. You’re going to assume they hold five gallons of kitchen scraps. But they don’t actualy have that much usable space, right? And then realize after a week on the road that you’ve got a full bucket plus a few bags of dry cover stuff. Half of it need to be tossed back in the trash bag to get the lid closed. Turns out the five gallon bucket wasn’t really five gallons of scrap space. It was just five gallons of physical container space, and this is where the plan goes wrong.

Why Your Compost Bin Size Is Wrong

You can also use that same formula to calculate how much waste you could handle on an overnighter with this handy dandy calculator. After entering your own bucket geometry and trip length, it calculates the rest for you. Saves you from guessing how much of that plastic volume actualy belongs to food peels.

The most important variable is not usually number of people. Most important variable is dry cover ratio. Pasta water, coffee grounds, fresh veggies makes a wet bottom that stinks when left uncovered. To absorb the moisture and kill the smell, you want some carbon rich material; sawdust, shredded paper, coconut coir etc. Problem is, that dry cover eats up valuable volume. If you’re using 35% dry cover by volume, you’ll have far less usable volume. That’s what folks tend not to account for. They size based off the wet stuff and then just ignore the dry stuff.

But what about bucket size? Turns out geometry is important too. While the same nominal label says “five gallon” whether you buy a rounded or boxy bucket, one uses much more interior space than another. A rectangular bin makes good use of corners wasted by round bucket. And a tapered pail has significantly less room around its base than a flat-top bucket of equal overall size. This tool understands those shapes and takes them into account, so you don’t have to guess based on nominal markings.

Even a five gallon pail marked on the side may only provide four gallons of storage capacity after considering headroom needed and the size of the lid mechanism itself. Leaving a 20% reserve at the top isn’t just nice, it’s required; there needs to be an air gap between the top of your pile and the bucket lip to allow stirring and avoid splashing. There needs to be room to expand when gases form during decomposition. And there needs to be that buffer zone to get the seal engaged. Otherwise you’re lugging around a bomb which will spill all over the place as soon as you drive across any bump in the road.

Weight is the other silent killer of good intentions. A bucket full of vegetable trimmings and coffee grounds can weigh as much as twenty-five pounds or more, which is pretty heavy for carrying around to the dump station, especially in an RV. The volume calculation is only half the equation, with weight being the other part. The other half is the filled weight estimate that will help you determine whether you’re up to the physical task. Most folks underestimate how heavy a wet mixture of stuff can get. When it’s dry (paper), it feels light. But once it soaks up some water from the scraps, it gets heavy fast.

And the length of your trip does make all the difference. If it’s a short weekend getaway, perhaps just a small countertop caddy will do? For longer trips like a week-long boondocking trip, something else needs to happen. You could use two smaller buckets instead of one big bucket. That way you can rotate through them. One is being filled up while the other is closed off to let things break down and settle. It helps reduce how often you have to empty them and keeps the smell more manageable than having only one giant bucket that fills up at the end of the week.

The tables on the page lay it out well for different group sizes. Another variable is the settling factor. Chopped scraps take up less space than whole fruit peels because they pack down tighter. You can increase your capacity by being diligent about chopping everything up, but that also makes it denser. Tradeoff: capacity vs. Convenience. Use this setting on the calculator to adjust based on how well you actualy do prep. Assume imperfect packing, unless you’re running a commercial operation.

You must balance weight against portability, capacity against lid integrity, and dry cover against wet volume. If you get the size correct, there won’t be any leaks or smells or back strain. It makes it a routine instead of a chore. Do the numbers, then tweak to fit your actual habits. Make sure to leave that headroom, because it’s necessary for the lid to seal and function properly. When you lift up that lid on day five, your nose (and your back) will thank you.