Published October 13, 2025 04:35AM
From their external-frame origins, modern hiking backpacks have branched out into forms multitudinous. Today, you can tote anything from gossamer frameless sacks to heavily-padded beasts with pivoting hipbelts and airy trampoline backpanels. But just as pack designs today vary, so do their load capacities: While some backpacks may tap out at anything above an ultralight load, others can carry your gear, your pets, and, probably, your partners without so much as leaving your shoulders sore. When you’re picking a pack, that’s essential information.
Every year, our testers put dozens of packs through their paces, carrying them with different loads and across a wide variety of terrain to figure out how they perform. But no two hikes are the same, and making apples-to-apples comparisons between how packs carry is difficult with just field testing. To get more information about how different popular backpacks transfer load between the hips and shoulders, we asked Outside Gear Test Editor Adam Trenkamp to devise a lab test to measure them directly. In this video, he walks you through how we got the data in this year’s pack test.
Hey there, I’m Adam Trenkamp, the lab test editor here at the Outside Lab in CU Denver. Today we’re going to talk to you about backpacking packs and specifically the load capacity of packs.
So in the lab, we like to look at everything with our gear, and one of the things we’re going to look at with packs is load capacity and effective load. So, when you wear a pack and you have a whole bunch of weight to keep you out in the backcountry for one night or 15 nights or, you know, six months if you’re doing a thru-hike, the hip belt is meant to carry a part of that weight. A lot of times what you’ll hear is the 80/20 rule. So 80 percent of the weight in your pack should be on your hips, 20 percent on your shoulders. That’s going to shift as you walk throughout the day and you hike, or even as you load your pack a little bit differently. But the theory stands: you should have more weight being held on your hips than on your shoulders.
So when we test for effective load, what we look for is when does too much of the weight slip past the hip belt and start to go on the shoulders, and that’s the effective load for each pack. Some packs are designed to carry more weight than others, and we want to find out which ones those are and how much weight each pack can carry appropriately.
Alright, let’s see how effectively Steve carries some weight here. We’re going to call him Steve. That’s his name for today.
That wasn’t very effective.
So to test the effective load of the packs, we use these flexible force sensors that plug into the computer via some USB cables here. So they read the force as it pushes down through the pack. To make sure we get the force around the whole pad when the backpack pushes down, we 3D printed some little knobs you can see stuck on top of the pad. That lets us read all four corners of the force sensor and make sure we’re getting a good representation of the weight through the shoulder pad.
So once we get our force sensor set up on our mannequin, we grab a pack and we get set up. You can see with some lines we’ve marked out where the top of the hip bones are for our mannequin. We use that to get our hip belt aligned with every pack.
Hip belt set. Alright, now we tighten our shoulder straps.
Once our backpack is fit, we go ahead and hook our force sensors up. Once we’re plugged in, we make sure our forces seem accurate, which is basically we shouldn’t be reading much force at all with just the pack because we have an empty pack. And then we zero out our load and start from there.
So we use some sleeping pads to stuff at the bottom of the pack. Typically this is where you’re going to pack your sleeping bag or your low-weight, bulky items to help push any heavyweight to the middle of your pack. Sleeping pads give us a little extra weight at the bottom of the pack, but still allow us to stack truly heavyweight on top. So, since we’re trying to test the actual effective load of the pack, if we just stuck some really low-weight, bulky items at the bottom of the pack, we’re going to have a harder time fitting a ton of weight in here. So by using these sleeping pads, each of these are about a pound and a half, we’re able to add three pounds to the bottom of the pack to start. And now we have some support for our heavyweight.
To do the test for all these packs, we start with a 13-pound weight. We record how much is being shown on the shoulders, and then we slowly add five pounds at a time after this.
So we keep adding weight to the packs until the force sensors on our shoulders tell us that more of the weight is actually being carried on the shoulders than the hips. So once that 50 percent mark shifts—even though we want to hold the 80/20 rule with only 20 percent on the weight of the shoulders as long as we can—we keep adding weight to the test until that 50 percent mark shifts and a majority of the weight is now on the shoulders. And then that’s our effective load point. So we can look at it as, what’s the best weight, but then what’s the true effective load of where does the hip belt fail and now a majority of the weight is on your shoulders.
So me and Steve here, we’re going to keep testing, but first I think he needs a little bit of a break and I’m going to help him get out of here. So we’re going to unhook Steve from science.
And we’ll see you—oh god, Steve, that’s so much weight. We’ll see you later.
