One-bag travel: pack for a month in a carry-on

Start with the system, not the bag

At Málaga Airport the train to the city takes the whole flight's luggage at once: wheeled cases tipped upright, packs still on shoulders. The people with the packs board and sit. That is the whole prize of one-bag travel, and you win it at home, weeks before the flight.

The bag is the last decision, and most people make it first. What actually holds a month together is a wardrobe of about two weeks, a wash day you have already chosen, a liquids bag built to 100 ml, and a short list of things you buy on arrival instead of carrying. Get those four right and 35 litres is generous. ⁸

Every figure below was read on 25 September 2026 on the page that owns it: Aer's product and warranty pages, IATA's baggage reference, the TSA and the European Union's liquids rules, three airlines' baggage policies, and two Bali laundries' price lists.

How do you travel with only a carry-on?

Five decisions, in the order that saves the most weight.

Work from the strictest airline on your itinerary backwards. The tightest allowance you will meet sets the bag; the bag sets the wardrobe; the wardrobe sets the wash rhythm. Reverse that order and you buy a pack that fits an American flight and fails a gate in Denpasar. ⁶

1. 01

   Find the tightest box you will fly

   Open the baggage page of every carrier on the trip and write down the smallest set of numbers. On this page that is AirAsia's 7 kg across two pieces, which is harsher than anything the dimensions will do to you. ⁶

2. 02

   Buy the bag to that box, with the empty weight in the sum

   A 35L pack that weighs 1.77 kg empty has spent a quarter of AirAsia's free allowance before a sock goes in. Volume gets the attention; the scale decides the argument. ^{1, 6}

3. 03

   Lay out two weeks, then remove the third of it you packed out of fear

   Two weeks of clothes plus a laundry service covers any length of trip. The month of clothes covers exactly one month and rides on your shoulders the whole time.

4. 04

   Build the liquids bag before the clothes

   One quart bag in the United States, one one-litre bag in Europe, 100 ml per container in both. Anything bigger goes on the buy-there list. ^{8, 9}

5. 05

   Name the wash day before you leave

   Pick the day of the week and the turnaround you will pay for. In Bali that is IDR 105,000 for a 3 kg next-day wash, booked with free pickup. A rhythm you chose at home beats a panic at 9 p.m. in a strange town. ⁷

The whole system rests on one bet: that clean clothes are cheaper and lighter to buy than to carry. In the places this page prices, that bet pays every time.

Which Aer bag: the 35L or the 28L?

Aer's Travel Pack 4 is the pick here on four stated grounds: carry-on fit on the airlines below, empty weight, clamshell access and warranty terms.

The Travel Pack 4 opens lay-flat, like a suitcase with straps. Aer's own page lists the clamshell main compartment and a suspended pocket that takes a 16-inch laptop. Packing cubes go in flat and come out flat, which is how a small bag stays organised through six hotel rooms. ¹

The 28L saves $20.00 and 0.38 lb and gives up 7 litres. Take it if your flying is mostly Asian budget carriers, or if you want the pack under the seat in front of you. Take the 35L if the month crosses seasons and a jacket has to come. Both clear every box in the next table. ^{1, 2}

Will your bag fit the airline you booked?

The industry reference is a courtesy. The airline's own page is the rule that gets enforced at the gate.

IATA publishes 56 x 45 x 25 cm as the size many airlines apply, and says in the same paragraph that allowances vary by airline, cabin class and aircraft. Where a weight limit exists, IATA's reference starts at 5 kg. Oversized bags get gate-checked, which undoes the reason you packed light. ⁴

The 35L pack clears all three boxes, one of them exactly. Turned on its side, 54.5 x 34 x 23 cm fits inside Volaris's 55 cm length with 5 mm to spare, and meets AirAsia's 23 cm face with nothing at all to spare. Soft sides and an empty front pocket are what get a packed bag into a sizer at that number, so pack the front flat on an AirAsia day. ^{1, 5, 6}

Read the fare class as carefully as the numbers. Volaris and Wingo both sell tickets that include only a personal item, so a pack measured to the millimetre still travels in the hold on the cheapest seat. MMT's country guides for Mexico, Colombia and Indonesia carry the arrival details for each. ^{5, 11}

What can you carry through security?

One hundred millilitres per container, on both sides of the Atlantic. The TSA writes it as 3.4 ounces or 100 ml per item in a quart-sized bag. The European Union writes it as 100 ml in a transparent bag holding at most one litre. For a traveller moving between them, that is one bag packed once. ^{8, 9}

The practical effect is a shopping list. Sunscreen, shampoo, conditioner, insect repellent and contact lens solution all arrive in bottles too big for the bag and too heavy for the scale. Decant a week of what you use daily into 100 ml bottles, and buy the rest within an hour of landing.

How does laundry work on the road?

The one line of spending that turns two weeks of clothes into a month of travel.

Washing is the whole trick, and in Southeast Asia it is priced by the kilo. Balilaundry.com lists IDR 35,000 a kilo for a 24 to 28 hour turnaround, with a 3 kg minimum charge and free pickup and delivery. So a standard wash costs IDR 105,000, and four of them carry a month. ⁷

Compare a second shop before you commit the month. CleanFold Bali in Canggu sets a minimum order of IDR 75,000 and adds 11% tax, which puts the floor at IDR 83,250 before weight. Its per-kilo rate lives inside a calculator on the page, so ask for the figure in writing for the weight you actually carry. ¹²

1. 01

   Day one: find the laundry before the beach

   Walk the block, photograph the price board, ask the turnaround. In Kuta and Canggu the shops advertise per kilo; elsewhere ask for the per-load figure and the minimum. ^{7, 12}

2. 02

   Day four: send the first load small

   Three kilos is the minimum charge anyway, so the first wash is a test at full price. Count the items out and count them back.

3. 03

   Every seventh day: repeat on the same day

   A fixed wash day is what lets you pack seven days of clothes instead of fourteen. Pick the day you are least likely to be on a boat.

4. 04

   Two days before you fly: send the last load

   Next-day service takes up to 28 hours, and a delay on the final wash is the one that costs you a flight's worth of clean clothes. ⁷

A monthly apartment with a machine changes this arithmetic again, and moves laundry into the housing column where it belongs. MMT's monthly stays against short bookings comparison sets out the rest of that trade.

What should you buy there instead of carrying?

Every kilo you carry in is a kilo you paid a weight limit for. The buy-there list is the cheapest weight saving on this page, and it costs you one errand on your first afternoon. ⁶

• Anything over 100 ml. Sunscreen, shampoo, conditioner and repellent fail the cabin rule at both the American and European checkpoints, and they are the heaviest items most people try to pack. ^{8, 9}
• Anything you will use up. Detergent, toothpaste, a razor. Consumables you carry from home get weighed at the AirAsia counter and then thrown away in week three. ⁶
• Beach towels and water shoes. Single-purpose bulk, in a bag you measured to the half centimetre against a sizer. ¹
• A third of your wardrobe. A month of travel in warm weather asks for about a week of clothes, a wash day and one spare set. The rest of what you laid out on the bed can stay there.
• Specialist gear, sometimes. Scuba and ski kit break the one-bag rule outright. Price the baggage against local rental first: MMT does the sums for flying with your own dive gear and for ski luggage fees against rental.

When one bag is the wrong answer

Three trips defeat the system, and it helps to know which before you buy the pack.

• Dive and ski gear are heavy and oddly shaped.
• A month across seasons means a coat that claims a third of a 35L bag.
• A suit in the middle of a trip goes in a clamshell, where it arrives creased however well you folded it.

Weight rules the edge cases. IATA's 5 kg reference leaves 3.23 kg once the empty 35L pack is counted, and a laptop claims a good share of that. Any airline that strict turns a one-bag trip into a personal-item trip, and the decision moves from what you pack to which fare you buy. ^{4, 1}

Everywhere else the maths holds. Pick the wash day before you pick the bag, and a month in the tropics is a pack you walk off the train with, both hands free.