The internet argues about 35L vs 40L bags like it’s a meaningful choice. It’s not. 35L wins on every metric that matters, and the only reason people keep buying 40L bags is because bigger feels safer.
It doesn’t make you safer. It makes you slower, heavier, and more likely to get stopped at the gate. Here’s why the debate is over.
Airline gate-check policies care about dimensions, not volume
IATA maximum carry-on dimensions are 55cm × 40cm × 20cm. That’s 44 liters of theoretical volume. But bags aren’t perfect rectangles, and airlines measure with sizers, not math.
Most 40L bags push 53cm to 56cm in height when packed full. They fit in the sizer when empty but bulge past it with a week’s worth of clothes. Gate agents eyeball bulge, not volume ratings.
I’ve watched this play out 30 times at budget airline gates. Ryanair, EasyJet, Wizz. The 40L bags get pulled aside for checking. The 35L bags walk through.
The difference is perception. A 35L bag looks intentional. A 40L bag looks like you’re trying to sneak a full suitcase past the rules.
The stuff-expands-to-fill-space law is real
Give yourself 40 liters and you’ll pack 40 liters. You’ll bring the extra sweater, the second pair of shoes, the “nice outfit” you’ll never wear, the book you won’t read.
Give yourself 35 liters and you’ll pack 35 liters. You’ll make real decisions about what matters. You’ll leave behind the hypotheticals.
I tested this directly. Two one-month trips, same season, same destination mix (three cities in Southeast Asia, humid climate). First trip: 40L bag. Second trip: 35L bag.
40L trip contents:
- 5 t-shirts (kept wearing the same 2)
- 3 pairs of shorts (wore 2)
- Sneakers + sandals + flip-flops (never wore flip-flops)
- Laptop + tablet (barely used tablet)
- Full toiletries (half came home unused)
- Two books (read one)
35L trip contents:
- 3 t-shirts
- 2 pairs of shorts
- Sneakers + sandals
- Laptop
- Minimal toiletries
- Kindle
The second trip was better. Not because I had less stuff, but because I stopped thinking about stuff. I washed clothes every four days and it took 10 minutes. The mental space I got back from not managing inventory was worth more than the convenience of extra shirts.
Real-world capacity testing
I’ve lived out of both bag sizes for months. Here’s what actually fits without the bag looking like a overstuffed burrito:
35L realistic max load:
- 5 shirts
- 2 pants
- 1 jacket
- Underwear and socks (7 days)
- Shoes (one pair packed, one worn)
- 13” laptop
- Toiletries
- Misc (charger, cables, Kindle, water bottle)
40L realistic max load:
- 7 shirts
- 3 pants
- 1 jacket
- Underwear and socks (10 days)
- Shoes (two pairs packed, one worn)
- 15” laptop
- Full toiletries
- Misc (same as above)
You know what’s not in the 40L list? Anything you actually need. The extra shirts sit at the bottom of the bag unworn. The third pair of pants is “just in case” inventory that never gets used. You’re carrying weight for optionality that doesn’t matter.
The 35L constraint forces clarity. You pack what you’ll wear, not what you might wear.
Weight comparison: the hidden cost
A 35L bag typically weighs 6kg to 7kg packed to capacity. A 40L bag hits 8kg to 9.5kg. That 2kg difference is the gap between walking 30 minutes to your hostel without stopping and needing a rest break halfway.
Budget airlines in Europe cap carry-on weight at 7kg. Ryanair, EasyJet, Wizz Air all enforce this with random spot checks. A 35L bag stays under. A 40L bag gambles every time.
Even airlines that allow 10kg rarely check, but when they do, a stuffed 40L is an easy target. Gate agents see the bulge and pull you aside. A neat 35L bag? You walk past.
The “I need space for souvenirs” fallacy
This comes up constantly. “But what if I buy things on the trip?”
You ship them home. Or you don’t buy them. A 2kg ceramic vase from a Portuguese market is not worth carrying for three weeks. Mail it for €20 or leave it on the shelf.
The extra 5 liters in a 40L bag is not free storage for your shopping habit. It’s wasted capacity you’re lugging around just in case you decide to become a souvenir hoarder.
If you’re traveling for six months and accumulate gear, ship a box home at month three. Don’t carry it all in a bigger bag from day one.
The bags we actually recommend
35L tier:
- Osprey Farpoint 40 (misleading name — it’s actually 38L, which is close enough): 1.1kg empty, bombproof build, laptop sleeve, hip belt. This is the default choice.
- Aer Travel Pack 3 (35L): 1.2kg, cleaner aesthetic, better organization, more expensive. Worth it if you value neat packing.
- Tortuga Setout Divide: 1.4kg, clamshell opening, divider system. Heavier but easier to pack if you’re OCD about organization.
40L tier we’d skip:
- Osprey Farpoint 55 (the actual 40L+ model): Too big, attracts gate checks.
- Nomatic 40L: Overbuilt, 1.9kg empty, filled with pockets you’ll never use.
The only reason to go 40L+ is if you’re carrying specialized gear (camera equipment, climbing gear, winter camping setup). For normal travel, it’s overkill.
What we’d do differently next time
I spent two years defending my 40L bag before finally downsizing. The 35L wasn’t a sacrifice. It was an upgrade. My shoulders hurt less. I walked faster. Gate agents stopped eyeing my bag.
The mental shift was bigger than the physical one. With less space, I stopped bringing “backup” items. I trusted that I could buy a replacement t-shirt in any city if mine got destroyed. I didn’t need a mobile closet.
If I could redo my first long-term trip, I’d start with a 35L and save myself two years of carrying unnecessary weight.
The verdict
35L is enough for one-bag travel unless you have a specific reason it’s not. And “I like having options” is not a specific reason. It’s anxiety disguised as preparation.
Go smaller. Pack less. Walk farther. That’s the whole philosophy.