The product page says 45 x 35 x 10 cm and 23 litres, and you still don't know if your A4 folder will fit. Look up the bag dimensions and you'll find outer measurements; the capacity in litres is the manufacturer's estimate, and the two figures regularly disagree with each other. With a tape measure and two rules of thumb, you can know within a minute what will actually fit.
Short answer: on a leather bag, subtract 1 to 2 cm per side from the outer size to get the inner size, and work out the litres yourself as height x width x depth in decimetres, times 0.7. Get a lower number than the manufacturer states? That's normal. Their figure is the bag full and bulging, your figure is the bag empty and flat. For choosing a bag, your figure is the more useful one.
Bag dimensions: how do you read height, width and depth?
Most webshops list the size as height x width x depth, though not all in that order. So look at the numbers themselves. The largest is the height on a backpack, the width on a weekend bag. The smallest is almost always the depth, and that's the one you can rely on least, since it changes the moment you put something in the bag.
Outer measurements are taken with the bag closed and empty, edge to edge, without the handles. With 2 mm leather, plus a lining, plus a seam that folds inward, you lose roughly 1 to 2 cm per side. A backpack 35 cm wide therefore has 31 to 33 cm of usable width inside. An A4 folder is 31 cm tall and 22 cm wide, a 15.6 inch laptop roughly 36 x 25 cm. That laptop won't automatically fit a bag 35 cm wide; it stands upright, so the height has to allow for it. On the 45 cm tall Mavis that's not a problem. On a 30 cm tall bag it is.
Depth is the trickiest. A bag with a flat 10 cm base takes up 10 cm empty, but easily bulges to 15 cm with a laptop, a glasses case and a lunchbox inside. Stiff vegetable-tanned leather gives less here than soft chrome-tanned leather.
How do you estimate the capacity in litres?
Divide the height, width and depth in centimetres by ten, multiply them together, then multiply the result by 0.7. That 0.7 corrects for the fact that a bag isn't a box: the corners are rounded, the top tapers, and some of the space is taken up by internal pockets. For the Mavis that's 4.5 x 3.5 x 1.0 = 15.75, times 0.7 is 11 litres.
The product page says 23 litres. You'll see that gap with nearly every brand, and it comes down to how it's measured. A stated capacity is usually taken from a filled bag, and a filled leather backpack isn't 10 cm deep but 18 or 20 cm. Put 20 cm instead of 10 into the formula, and you land on 22 litres, which suddenly matches. So the formula with the flat depth gives you the capacity before the bag starts to bulge. That's what you plan around if you're carrying a laptop, since you don't want to wedge one into a bulging bag.
Use litres mainly to compare bags within the same brand. Between brands they say little, since one measures full and another measures flat. Comparing two brands is better done on the dimensions themselves: bag against bag, in centimetres.
What does 20, 25 or 55 litres mean in practice?
Twenty litres is the daily backpack. A laptop up to 14 or 15 inch, an A4 folder, a glasses case, a lunchbox and a half-litre bottle. A second folder can still go in, a thick jumper can't. It's the size for the office, lectures and the city.
Twenty-five litres sounds like a bit more, but it's a quarter more space. In practice that's the difference between a laptop plus a folder, and a laptop plus a folder plus gym kit or a 1.5 litre bottle. Anyone heading to the gym after work will notice those five litres every day. Anyone only carrying a laptop is hauling around five litres of air and a bag that never sits taut.
Fifty-five litres is a different kind of bag altogether. That's a weekend bag: clothes for two to three nights, a wash bag, shoes on top and a bit to spare. The Milo at 55 x 27 x 25 cm sits in that category. Run it through the formula and you get 5.5 x 2.7 x 2.5 = 37, times 0.7 is 26 litres flat. Full and bulging, that doubles. For a weekend that's plenty. For a week with laundry to bring back, it gets tight, and you're better off looking at a suitcase.
Beocca sizes and their litres
The table sets the outer dimensions from the specifications against the stated capacity and against the result of the formula with the flat depth. That last column is deliberately the low estimate: what fits before the bag expands.
| Model | Type | h x w x d (cm) | Stated capacity | Formula, flat |
|---|---|---|---|---|
| Cleo | Backpack, laptop up to 14 inch | 25 x 32 x 11 | 20 litres | 6 litres |
| Lorne | Backpack, everyday use | 30 x 26 x 8 | not stated | 4 litres |
| Lilith | Backpack, vintage style | 40 x 35 x 12 | 20 litres | 12 litres |
| Mavis | Backpack, laptop up to 15.6 inch | 45 x 35 x 10 | 23 litres | 11 litres |
| Finn | Backpack, laptop up to 17 inch | 40 x 35 x 12 | 25 litres | 12 litres |
| Bryce | Backpack, laptop up to 17 inch | 43 x 29 x 12 | 25 litres | 10 litres |
| Milo | Weekend bag | 27 x 55 x 25 | 55 litres | 26 litres |
| Ivy | Shoulder bag, tablet up to 10 inch | 23 x 29 x 8 | not stated | 4 litres |
| Beau | Handbag | 22 x 28 x 12 | not stated | 5 litres |
What stands out: the gap between the formula and the stated figure is biggest for Cleo, and that makes sense on a compact model, since every centimetre the bag expands counts proportionally more there. Finn and Lilith share the same outer dimensions, but Finn is built around a 17 inch laptop. Bryce is narrower than Finn (29 against 35 cm) and a bit taller; a 17 inch laptop fits both, but sits more snugly in Bryce.
What should you measure at home before you order?
Take the largest thing you carry daily, usually a laptop or an A4 folder. Measure it in its case, since the case counts too, and compare it with the inner size: outer size minus 2 cm per side. Fits on paper with 1 cm to spare, and it'll fit in real life too. Fits exactly, and it won't, because leather barely gives sideways and a zip you have to force over a laptop will fail within a year.
Then look at the depth, and especially at what else needs to sit next to the laptop. A 2 cm laptop, a 4 cm glasses case and a 6 cm lunchbox add up to 12 cm. At 10 cm deep that only works if the bag bulges, and then your laptop sits at an angle. At 12 cm it fits neatly. More on that trade-off is in our guide to choosing a leather backpack for work and free time, and anyone still torn between a backpack, a shoulder bag and a tote can turn to the general buying guide for leather bags.
Want the bag to fly as hand luggage? Then different measurements apply than those of your belongings. How many litres fit in the overhead locker and which sizes airlines use is covered in how many litres a backpack may be as hand luggage.
One mistake people often make: buying a bag for the busiest day of the week. Anyone carrying gym kit once a week and only a laptop the other four days spends those four days with a half-empty bag that hangs limp and lets the laptop slide around. Buy for the ordinary day. A bag the size of the Mavis then sits taut, and a weekend bag like the Milo is there for the days it genuinely is a lot.
