UKC

I have noticed in some reviews that "the rucksack feels more like 30l rather than being 35l, as stated" or something similar. I also heard that one company says the rucksack is larger than it really is, hence the weight:volume ratio looks better. Meanwhile, I always thought that's just some feeling-based argument against/for a company.

Now I found almost identical rucksacks, Oxford Aqua 25R ( http://oxford-products.com/us/products/Aqua-25R-Back-Pack.html ) and Lomo 30l ( http://www.ewetsuits.com/acatalog/drybag-daypack.html ). Given Aqua 25R has an additional mesh pocket on the side, no matter how you measure the capacity, you can't get less than the obviously same rucksack!

Okay. It does not matter which volume is the right one (I believe it's over 25l as I manage to squeeze more things into Lomo 30l bag than into other 25l rucksack). But how do companies measure them?
1. Does the rucksack have to be closed in order to measure the volume (very actual for roll top design)? It's quite clear when there's a floating lid involved and then company provides two numbers.
2. Do external pouches count?
3. Do hip belt pockets count?
4. What does not count?
5. If there are different sizes for the rucksack, which size to use? Some manufacturers provide information for each size, but still claim the same volume in the name of the sack.
6. Can the number be rounded or more realistically, by how many litres? There are so many 40l, 60l or 70l rucksacks and I'm certain they are not exactly that.

Of course, PPE stuff must be regulated and tested. It's not enough to claim that the sling is rated to 22kN - you have to prove it. Clearly, volume of the rucksack is not so life-dependant and no one will find out whether it's 32.3l or 37.6l.

In reply to PPP:

Different companies use different methods, some may actually measure the volume!

I'd say that external and lid pockets count towards the total volume but not necessarily those on hip belts. To my mind you should be able to close the sack to enclose the stated volume.

The easiest way to check the volume is to put a flexible waterproof bag in to the sack and fill with water until you reach the "full" level. You just have to weigh the sack before and after filling with water - since 1 litre of water weighs 1 kilogramme the difference in weight is the volume.

In reply to PPP:

My gosh - I hope this isn't a major concern. If so I'd get out more!

In reply to PPP:

Yeah, but mine goes up to 11...

In reply to PPP:

In the good old days sacks were advertised as "60+15" where the first number was the volume of the main compartment and the second was the volume of the pockets.
It would be great to see a standardised test for measuring sack volumes - I'm guessing using small balls (plastic BBs?) would be best.

In reply to Toerag:


You sure? Because that 'plus' system's commonly used for sacks with extending tops.

In reply to Toerag:

I was told more than once that karrimor used to use dog biscuits to measure the volume of their rucksacks, as someone who worked there had a guide dog. If it was a labrador, filling a pack up with biscuits and fastening the lid would aslo be a good way of testing it's durability. >1min = lifetime guarantee.

In reply to Toerag:

I wouldn't use ball sacks to measure volume me, all sorts of problems with that approach.

In reply to PPP:

I think Alpkit use socks?

In reply to petestack:


That as well - I've had sacks with non-extending lids that were designated in that way though, so it's not purely for extending lids.

In reply to andrewmcleod:



Is a litre of socks less or more than a litre of Winalot Shapes?

In reply to PPP: Loads of posts but no one has mentioned that there IS actually a standardized way of measuring rucksack volume.

The forward thinking ones will use the American ASTM F2153 standard http://www.astm.org/Standards/F2153.htm where volumes are measured using 20mm solid plastic spheres.
The rest basically pull a number from thin air that is generally worthless.

I have not paid my $38 for a full copy of the standard but as far as I know, yes, yes and yes.

From the link above:
"1.3 This test method does not take into consideration areas of the backpack that are not completely enclosed by fabric such as mesh pockets, water bottle holders, and compressor pockets."

Not sure, but I presume the standard will cover it.

As above, not sure but I presume the standard will cover it.

In reply to PPP:
Don't know how they measure Litres but I've had 2 climbing sacs from Aiguille (the second was made to order) and they have a reputation, borne out by my own experience, not only for high durability without lots of nonsense features but also of delivering the litres they state. Can't recommend them highly enough and my only connection is that I live in the county where they are made and am a very satisfied customer. The only sacs I've ever had that have lasted 10 years or more of constant use.

In reply to PPP:

Socks. https://www.alpkit.com/support/stickies/how-do-we-measure-volume