Bag volume

[Abby]

So I've been mulling over the idea of a Maker's Bag since it came out. One of the things that held me back was the volume of 12.5 liters--half a liter less than the 13-liter Pilot, which to me feels more compact, and only half a liter larger than my DLBC, which I find too small for most uses. I looked at the measurements and realized that the width and height of the MB are a smidge bigger than that of the DLBC, but the depth is almost twice: 6.9" to the DLBC's 3.3". Shouldn't that mean that the volume of the MB is over twice the volume of the DLBC?

If you do the math on the DLBC you get 7.23 L. On a MB, you get 15.4. Then I started looking at the volumes and measurements of other bags I own and realized that the LCB has a posted volume of 11 liters but width x length x height gives you 9.5. Doing the math on a Pilot gives you 14.7, not 13. What gives? Have I been calculating volume wrong all these years? I remember reading somewhere that TB calculates volume by filling the bags with plastic balls or some such. Are the external and internal measurements really that different?

[brucep]

I remember reading somewhere that TB calculates volume by filling the bags with plastic balls or some such.

Note the ASTM link on the product pages.

Edit: OutdoorGearLab tested an Osprey Exos 48 with the same methodology.

[Abby]

The link takes you to a page where you can purchase a PDF of the test method for $39.00. No other explanation that I can find.

I'm finding it hard to imagine how volume could be measured in such a way that MB/DLBC volumes are almost identical, when according to external measurements the MB is twice as big.

[loma]

I'd also like some clarification about the MB's dimensions. The product page says the bag is 10" tall and 6.9" deep, but in the pictures the side panel don't look like they're as wide as more than half the height of the bag. Are the side panels actually 6.9" wide?

[nukediver]

My suggestion is to not get hung up on the specific volume of the bags. Over the years I have found that the only way to really understand it is to have the bag in your hand, and to pack it with your stuff. I know that isn't always a practical option, but maybe you can search the forums for pictures and packing lists for the MB for a better idea of its capacity (there were lots getting posted right after the bag's debut).

I have had all three of the bags you mention, and actually found the MB to hold more than the Pilot, but that was specific to my stuff. I tend to carry a lot of papers and a tablet, so it was just easier for me to flip open the top flap of the MB and access everything than it was to unzip all the pockets on the Pilot to get to everything I needed. But if it's security of the items that is your concern (like having the bag flop over and disgorging the contents) then the Pilot might be better.

[brucep]

I'd also like some clarification about the MB's dimensions. The product page says the bag is 10" tall and 6.9" deep, but in the pictures the side panel don't look like they're as wide as more than half the height of the bag. Are the side panels actually 6.9" wide?

About 5" between piping at the bottom, and 4.25" between piping at the top. Of course, the front and back extend beyond that.

[loma]

Thanks brucep, that's very helpful. So 6.9" is approximately the depth of a stuffed bag in the center?

If you can, would you mind telling me the height and width of the front panel? I'd like to be able to make a mockup of the bag, kind of like this.

[tpnl]

The front panel dimensions on my MB are the same as the website: 13.6 x 10 inches. This measurement is taken piping to piping - so to speak.
The depth of my MB is 5.5 inches bottom piping to piping.

I agree that the key here is the the Pilot cannot expand as much as the open topped MB and this is where I think the feeling / reality that the MB can be stuffed more and therefore hold more comes from.

Hope this helps
Cheers

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Edit:
The volumes of the MB, DLBC and LCB have been updated:

MB – 14 L / 855 Cu in (more than a Pilot or Cadet)
DLBC - 9 L / 550 Cu in (same as Ristretto but not as much as a LCB)
LCB – 10 L / 610 Cu in

Note that soft sided bags can be overstuffed and may seem to hold more – unlike hardsided luggage

[kayaking]

I hope the photos attached. Amy, I thought these might be helpful. The only things you can't see in the picture are my iPad and phone. My EDC for the last month. Without water in the bottle it comes in at 7.5 lbs. I don't usually carry the iPad (have a presentation tommorrow). It has enough room for me to throw a pair of sandals on the top. I often wear my sneakers for the commute, but since I'm carrying a second bag with books for the presentation they're separate.