Please sign in to post.

Help determining capacity in litres

I am going to buy a 2 wheeled bag with knapsack straps (looking at the Osprey Fairpoint 65L) for my next trip to replace the suitcase that broke on my recent trip but can't for the life of me figure out how to determine capacity in litres! I want the new bag to have the same carrying capacity of the old suitcase which is 18" wide, 10" deep and 27.5" high. Can anyone here tell me if that means it has a 55L capacity? If not, any idea how to calculate this?

Thanks very much.

Posted by
943 posts

Ask google. Ask Siri. There are dozens of online calculators. Every luggage description offers metric and royal measurements and volumes. 10x18x28 inches equals 5040 cubes, about 82 liters. 1 cubic inch equals 16.4ml, 1000ml in a liter. 55L is about 3360 cubes.
unitconvertors.net

Posted by
6016 posts

You can get a rough idea with the calculations above, but makers of packs and baggage seem to use magic math to get their volume sizes. Differences such as expandable sections can also add confusion. Overall, I would say the Osprey is similar in size, but narrower and deeper. I guess rather than brute capacity, you might want to compare the size to allowances for outside dimensions of the airlines you travel. But that does look like a nice bag.

Posted by
3348 posts

1 litre = 1 dm3 = 1000 cm3.

I.e. convert the dimensions to centimetres, multiply them and divide by 1000. That will give you a rough estimate.

Posted by
5570 posts

You didn't say, but you may also wish to check compliance with your most frequent airlines' exterior dimensions. That's what, theoretically, could keep a carry-on OFF the plane.

Posted by
13716 posts

So, you are going to back pack a check only bad you know; and that's okay.
As for the capacity, since you are trying to be accurate, those dimensions, if published, may be including the wheels so they dont represent the inside dimensions (unless they say they do).

Posted by
943 posts

We saw on asimilar thread the Farpoint and Fairview Ospreys were out of stock planet-wide.

Posted by
18377 posts

Use 61 cu in. per liter. That's very close; it's 61.02 ci, actually).

27½" x 18" x 10" = 4950 cu in, or 81.15 L (or is that 81,15 L?).

Calculating the capacity of a bag is a black art. I've seen many bag advertisements in which the stated capacity is greater than the outside dimensions. I guess the bag companies just stuff the bag with some sort of "flexible" solid, like beans, then empty the bag into a measurable container. Unfortunately, the sides bulge to where it would not fit into a sizing frame for a carryon bag.

The outside dimensions of a regulation bag for most airlines is 22" x 14" x 9" or 2772 cu in. That's just over 45 liters. But I once figured, taking into account the weight of the empty bag if it is all nylon cloth (not a roll aboard), that you lose another 1½ to 3 liters due to the volume of the bag itself, so maybe a regulation backpack bag is more like 43 liters. You lose a lot more than that with a two-wheeled roller bag due to the space lost to the wheel and handle cavities, and even more with a spinner.

Posted by
978 posts

"Calculating the capacity of a bag is a black art"

Seems so!

Here's what Eddie Bauer has to say about my Expedition Rolling Duffel - Large:

Capacity: 4,088 cu. in. / 67L || 26"L x 16"W x 14"D

And those dimensions are pretty bang on to a 30-year-old regular Eddie Bauer duffel bag I have - but the new bag holds less than the old bag.

Periscope,
I hear ya! Design has a big impact on volume. Volume of a simple, one compartment, rectangular case is easy to determine. Computer compartments, padding, depth of pockets, etc. - all these things affect volume. I prefer simpler backpack and suitcase designs for this reason. Also, if there’s an outside water bottle pocket, the luggage/bag company may count that as part of the overall volume.

I have purchased a couple of bags/organizer pouches and after receiving them, truly wondered if anyone
at the company actually tested the product prior to production. There are some lemons out there.

Posted by
943 posts

Measuring bags is not a dark art at all; it's just math.
Do not confuse capacity with volume.
Do not confuse the outside dimensions with either capacity or volume.
Wheelies are described -- by reputable makers -- using the outside dimensions, including the transmission and handles, since these will determine if the bag is international or domestic carryon legal.

The total internal volume of that same bag cannot be determined by those outside dimensions because of the construction methods and the loss of internal space occupied by the wheels and support structures for the handle. Carrying capacity is further reduced by internal pockets, flaps, and other stuff.
Osprey provides appropriate and accurate numbers and their customer service can answer your deeper questions. However, good luck finding the bag you want! Osprey's website currently lists Farpoint and Fairview as OUT OF STOCK. Here in Boise, Idaho, three stores carry Osprey luggage: REI had one Fairview on the floor a few weeks ago, Idaho Mtn Touring has zero, and I haven't checked with the other one.

https://www.osprey.com/us/en/retailers/

Posted by
11441 posts

There is an industry standard as to how volume is measured in bags.

Tiny plastic pellets--usually 20mm--are loaded into a bag. It is filled to capacity. Then the pellets are put in a measuring device, usually a tube, and the company sees the reading in liters. With this number, they can figure out capacity in cu inches.

How can some bags hold more than the dimensions state? Simple. Soft sided bags are pliable and stretch. Therefore, then can hold more than the dimensions.

Not all companies use this technique. Some just multiply L x W x H. (Like RS.)

Posted by
943 posts

There is an industry standard as to how volume is measured in bags.

My favorite technique is a guy on the yootoobs that crams cans of beer or soda into his bags. then he stacks the the cans. It's not exactly useful but terribly amusing.

Posted by
1940 posts

Do you suppose the 65L in the name of the bag (Osprey Fairpoint 65L) means 65 liters??

Posted by
11441 posts

Do you suppose the 65L in the name of the bag (Osprey Fairpoint 65L) means 65 liters??

Yes, that's exactly what it means

Posted by
18377 posts

Soft sided bags are pliable and stretch. Therefore, then can hold more
than the dimensions.

But if the outside dimensions are right at the regulation size for a carryon, then over-filling it and bulging the sides will probably mean that the bag will not fit in the sizer. In this country, the regulation size for a carryon is 22" x 14" x 9", or 2772 cu in (45½ L). If you try to fill it to more than that volume, the bulging side will probably be cause for rejection in the sizer. And remember, just the nylon cloth that bags a soft bag probably occupies 100-200 cu in, so the actual capacity is less the 44 L.

Do you suppose the 65L in the name of the bag (Osprey Fairpoint 65L)
means 65 liters?

Yes, that is probably what it means, but the overall dimensions of the Fairpoint 65, 70 x 41 x 34 cm gives an outside envelope of 97.6 L. But it's not a rectangular solid, and the volume lost to bulging pockets, the wheels, and the handle tunnel takes away from the outside envelope. I would assume that the 65 L is an honest capacity calculated as Frank describes above.

Posted by
31521 posts

The "dark art" isn't really too hard to figure out. If you have an iPhone, just ask Siri how many cubic inches a set number of litres is.

Posted by
13716 posts

Or line the bag with plastic and start pouring water in. Or do carryon and only fly airlines with a 8kg weight limit. You will never fill the bag before you hit 8kg.

Posted by
943 posts

Do you suppose the 65L in the name of the bag (Osprey Fairpoint 65L) means 65 liters??
Yes, that's exactly what it means

That's funny. How difficult is this stuff to figure out? From the Osprey website:

VOLUME DIMENSIONS WEIGHT
O/S 3,967 IN3 / 65 L 27.56H X 16.14W X 13.39D IN. 6.17 LBS.

Posted by
978 posts

From the Eddie Bauer website:

Capacity: 4,088 cu. in. / 67L || 26"L x 16"W x 14"D

Posted by
18377 posts

How difficult is this stuff to figure out?

Apparently pretty difficult. Note there is a 1½" difference between Osprey's overall length (27.56") and Eddie Bauer's measurement of the same thing (26"); might be that EB didn't include the handle (or wheels). Osprey's website also gives the dimensions in the metric system, 70L x 41W x 34D, in cm, which converts to 27.56" x 16.14" x 13.37", but I really doubt that Osprey's manufacturer really cuts the fabric to the nearest 1/100th of an inch. The bags are probably made in China to the metric system, maybe to the nearest cm, ±0.5 cm (0.2"), if that.

But the Osprey 65 bag does not do a very efficient job of using their overall dimensions, which, converting from the metric overall dimensions they give is about 97 liters, but both EB and Osprey estimate the capacity at around 65L.

Posted by
11973 posts

I don't stress too much over size. I make sure the external dimensions of my bag meet airline allowances. Done; now I know the size of my bag.

My focus is on the weight of what I'm carrying. I'll stay under the max weight the airline allows. But I don't stop there. I work to get it down to something I can comfortably carry rather than the absolute max allowed.

Actually, I've gone way past that. Rather than bring the maximum size carry-on my airline allows, I now bring a carry-on that fits every airline's allowance - even Ryanair. And I've decided I'm overjoyed keeping my bag at 10 lbs. (but I allow myself 12 Lbs. max).

I've carried no more than that for multiple 17 to 21-day vacations and been happier for it. Not only is it possible, it's also preferable.

Posted by
28107 posts

Travel Boss, you should travel with Lee. You could have a competition for light and cheap.... LOL

Posted by
943 posts

I've carried no more than that for multiple 17 to 21-day vacations and been happier for it. Not only is it possible, it's also preferable.

The elegant practicality of carryon-only travel is often lost in the discourse over the philosophy, Or is it the other way 'round? Unless you are holding onto them, arriving with one's luggage is a binary event, unaffected by all previous events or the experience of others: your bags are there or they are not.