This question can definitely lead you on the wrong path. If you start with this question, then the answer can likely be something like:
"I am traveling far away so I need a large suitcase."
This is a kind of subconscious logic that I have often heard people follow. But after all, why? If you are going to spend your whole holiday at the beach in a swimsuit, you hardly need to bring anything! There is definitely no relation between distance traveled and suitcase size!
"I have a 50lb luggage allowance so I will fill my suitcase to the limit".
"I am entitled to a 22"x14"x9" carry-on luggage so I will make sure my bag is not an inch shorter".
"In addition to my carry-on bag, I may take a small handbag or computer case so I will".
I think you see my point by now: do not let external contingencies determine the size of your bag.
"I will be away a long time so I need a very big bag!"
Hmmm. And, pray, why is that?? Try to be sensible: if you will just carry this bag for five minutes, then yes, it may be OK to have a big one. But what if it is going to follow you a whole week? or a month? Do you want to be carrying weight around all the time? Of course not. You want your luggage as small as possible, not big.
Try reversing the logic completely:
"Bag? I don't need any bag!"
If I'm traveling for a day or two, I can surely survive with just a toothbrush and a phone charger. Does that fit in my pockets? Yes. Aha! Bag stays at home!
"What did you just say? Toothbrush? I am pretty sure they have toothbrushes at that hotel!"
Aha! Toothbrush stays at home!
At that point, you can almost hear all your stuff screaming: "How can you possibly do that to us???"
Be strong! Resist the urge! The first time may be hard but afterwards you realize the obviousness of it:
YOU are traveling, not your stuff. Regain control!
Let us be realistic, there will be occasions when you will want to carry a bag. In that case, make sure you are still the master. Select a good, small travel bag and work from there: how much fits in there? What doesn't fit will stay home, and you'll probably survive.
My bag is a small sports backpack.
Backpacks are far better than suitcases:
- they leave your hands free while walking, meaning you can walk faster and even ride a bike with your backpack on (or go to the bathroom),
- they let you use staircases rather than crowded escalators in airports and malls, so that you get ahead of everyone,
- and it is much more comfortable to carry weight on your back than to lift a suitcase. Roll-on suitcases are OK in airports or for short distances. But on the rough pavement of some foreign cities, or worse, in the wild, backpacks are the only realistic choice.
Regarding the size, my criterion is: must fit comfortably under my airplane seat (behind my legs). This way:
- I never have to fight for carry-on space,
- I also make sure my bag does not get too heavy, even when full. And when empty, it hardly weighs anything. I guess by now you have found out: I hate weight.
My current bag measures 16"x11". It could be a bit larger and still be OK. And it is quite extensible in thickness: when completely filled and deployed it can reach almost 10" and that gives quite some room.
The other good thing about a small bag is that it routinely exceeds the 20lb weight limit for carry-on luggage on planes, but it looks so small that nobody ever cares to check.
I know it looks a bit flabby and worn, but please use a little respect: this little guy has probably traveled close to 200 000 miles, and it is also my everyday bag to go to work. But yeah, it sure is nearing retirement age...
The nice thing is that, despite its small size, the storage space is well divided, including:
- a main pocket (actually divided in 2), where I will usually store clothes and my laptop if I carry it,
- a middle pocket for toiletries, underwear, laptop charger and small stuff,
- a smaller front pocket for travel stuff which basically stays there all the time,
- side flaps which come handy to keep a bottle of water or a hat, etc.