The failure mode is not forgetting things
Almost everything you could leave behind is sold at your destination. Toothpaste, a phone cable, a rain shell, underwear, a razor — forgetting these costs an errand and some money, and the errand is often more interesting than whatever you had planned for that hour anyway. Packing anxiety is mostly spent on this category, which is the category that does not matter.
The items that actually ruin days share one property: they cannot be obtained quickly where you are going. A prescription requires a local prescriber. Prescription glasses require an exam and a lab. A proprietary charger for a medical device or an old camera requires a specialist shop that may not exist within a hundred miles. A passport requires an embassy appointment and days you did not budget. None of these are expensive items. They are slow items.
So the question to ask about every object is not "will I use this" but "if this were not in the bag when I arrived, how many hours would it take to have one again". Sort the list by that answer and the top of it looks nothing like the top of a normal packing list.
The four tiers
| Tier | Examples | Where it goes |
|---|---|---|
| 1 — Cannot be replaced on the trip | Prescription medication, passport and other identity documents, prescription glasses and contacts, medical devices and their specific chargers, hearing aid batteries, custom orthotics, the one key or fob you need to get back into your own house | On your person or in the bag that never leaves your hand. Never checked, never in an overhead bin two rows away, never in a car trunk overnight. |
| 2 — Replaceable, but slowly or expensively | Laptop and its charger, camera bodies and lenses, a well-broken-in pair of hiking boots, a CPAP mask, specialized sports equipment, anything with sentimental value | Carry-on where size allows. If it must be checked, photograph it first and keep the serial numbers somewhere you can reach without that device. |
| 3 — Replaceable in an hour, for money | Clothes, toiletries, a common phone cable, an umbrella, sunscreen, a book | Checked bag. Do not spend planning time here. |
| 4 — You are not going to use it | The third pair of shoes, the second jacket for the one cold evening, a hair dryer, "just in case" gear for an activity you have not committed to | Leave it. Most overweight bags are made entirely of tier 4. |
The useful discipline is doing tier 1 first, physically, before anything else goes in a bag. Lay those items out on the bed, count them, then pack them. Everything after that is comfortable.
Carry-on: the first 24 hours
Assume for a moment that your checked bag arrives a day after you do. This happens to a small but non-trivial share of travelers, it is more likely with a tight connection, and it is entirely survivable if you packed for it. The test for the carry-on is simple: could you get through a full day and a night, and attend whatever you flew there for, out of this bag alone?
| Category | In the carry-on | Why |
|---|---|---|
| Medication | The full trip supply if it fits, in original labeled containers, plus a written list of drug names and doses | A pharmacist in another country needs the generic name, not the brand you know. Splitting doses across two bags is a common piece of advice that fails badly when the bag with half the supply is the one that goes missing. |
| Documents | Passport or ID, whatever entry paperwork applies, insurance details, a printed copy of your first night's reservation | Battery-independent. Photographs of documents on your phone are a good backup and a poor primary. |
| One change of clothes | Underwear, a shirt, and whatever you would need to look presentable | This is the single highest-value item in the bag if the checked bag is late and you have a meeting, a wedding, or a funeral |
| Toiletries | A minimal kit, subject to whatever liquid rules apply on your route | Volume and container limits differ between screening authorities and change over time. Check the rules published by the authority at your departure airport shortly before you fly rather than trusting a number you read once. |
| Power | Phone charger, a cable per device, a power bank | Lithium batteries and power banks are generally treated differently from other items and are usually restricted to the cabin rather than checked baggage — but the specifics vary by airline and by capacity, so confirm with your carrier. |
| Glasses | The spare pair, and the prescription itself | The prescription written down turns a week-long problem into an afternoon |
| Valuables | Everything you would be upset to lose | Airline liability for checked baggage is limited and the limits differ by route and fare. Do not put the argument off until you need to have it. |
Bag trackers
A small Bluetooth or satellite tracker in the checked bag changes the character of a lost-bag conversation. Instead of asking an agent what the system says, you can tell them the bag is at the airport you departed from, or that it is sitting in a facility eight miles away. That is not a magic solution — you still go through the same claim process — but it converts "we do not know" into a factual disagreement that gets resolved faster.
Put a second identifying card inside the bag as well as on the outside tag. Outside tags come off in belt machinery constantly. A card inside with your name, phone number and email is what a handler reads when a bag arrives with no tag at all, and it costs nothing.
Weight, volume and the bag itself
Checked and carry-on allowances are set by the airline and often by the fare class within that airline, which means the numbers you memorized on a previous trip may not apply to this ticket. Weigh the bag at home on a bathroom scale — stand on it holding the bag, subtract your own weight — rather than discovering the problem at a counter where the fix costs money and the queue is behind you.
Two practical notes that survive whatever the current numbers are. Hard-sided cases protect contents and cost you the flex that gets a bag into a sizer. Soft cases squeeze but transmit impacts. And a bag that weighs eight pounds empty spends eight pounds of your allowance on the bag; if you are close to a limit regularly, the lightest case you can find is the cheapest weight you will ever buy.
Packing cubes do not save space, whatever the marketing says — compressing clothes into a cube and then putting the cube in a suitcase generally uses about the same volume. What they do is make the bag searchable, so that living out of it for two weeks does not degrade into an archaeological dig. That is worth having on a long trip and pointless on a weekend.
Medication, honestly
Keep medication in the original labeled containers. Carry a written list with the generic names, the doses and the prescribing clinician's contact details, because brand names are not consistent internationally and a pharmacist abroad cannot work from a picture of a pill.
Here is the part that a travel page cannot resolve for you: some medicines that are entirely ordinary in the United States are controlled or prohibited in other countries, and that includes some common stimulants, some painkillers, and some cold remedies. Nobody can give you a reliable current list, because it changes and it differs by country. The correct source is the destination country's own embassy or health ministry, checked before you go, and your prescriber if you need a letter. Do not take a forum post as authority on this.
Electronics and power
Count cables, not devices. The failure is almost never a forgotten laptop; it is a forgotten proprietary cable for a camera, a watch, a hearing aid, or a device that predates the current standard. Anything that does not use the same connector as your phone gets its own line on the list.
Plug shape and voltage are two separate problems. A plug adapter changes the shape; it does not change the voltage. Most modern laptop and phone chargers accept a wide input range and are fine anywhere with the right adapter, and that is printed in small type on the brick. Hair dryers, curling irons and older appliances frequently are not, and plugging a single-voltage appliance into a higher-voltage supply destroys it immediately. Read the brick before you decide whether you need a converter or only an adapter.
The list you actually keep
The good list is not downloaded. It is the one you edit the evening you get home, while you still remember what you carried the whole way and never touched, and what you had to go out and buy. Two edits per trip and within a few trips you have a list that fits how you travel, which no generic list ever will.
Keep it somewhere you can duplicate — a note, a doc, a template you copy at the start of each trip. Keep separate versions for the trip types you actually take rather than one master list with everything on it, because a list with sixty items you skip trains you to skip items.
The whole tier system exists because bags occasionally travel without their owners, which is a separate problem with its own procedure — see delays and baggage for what to do when it happens.
One sentence to take away: pack tier 1 first, on the bed, before any clothes go in the bag, and everything else is a shopping trip at worst.
Questions people ask
What should never go in a checked bag?
Prescription medication, identity and travel documents, prescription glasses or contacts, medical devices and the specific chargers they need, keys, and anything you would be genuinely upset to lose. The organizing idea is replaceability: a shirt is a twenty-minute errand at your destination, and a prescription is a local prescriber, an appointment and possibly a country where that drug is not available. Airline liability for checked baggage is limited, and the limits differ by route, airline and fare, so this is not a category where you want to find out the specifics after the fact.
How much liquid can I bring in a carry-on?
That is set by the screening authority at your departure airport, and it has changed more than once as scanning equipment has been upgraded — some airports have relaxed the rules and others have not, sometimes within the same country. The only reliable answer is the one published by the authority that will actually screen you, checked in the week before you fly. Whatever the current limit, the practical move is the same: keep the liquids kit small and near the top of the bag so a secondary check costs you thirty seconds.
Should I split my clothes between two bags in case one is lost?
Split clothes if you like — it is harmless. Do not split medication, which is where this advice usually gets misapplied. If half your supply is in the bag that goes missing, you are still short. Keep the whole medication supply in the bag that stays with you, along with one full change of clothes and anything needed for the reason you traveled. The goal is that a delayed bag costs you an inconvenience, not a plan.
Are packing cubes worth it?
They do not save space, despite what the packaging implies — compressing clothing and then putting the compressed block in a suitcase takes roughly the volume it took before. What they buy is retrieval: you can find one shirt without unpacking the bag, and repacking in a hotel room at six in the morning takes two minutes instead of fifteen. On a two-week trip with several hotels that is genuinely useful. On a weekend it is an extra step for nothing.
Can I bring my medication into another country?
Usually yes, and sometimes no, and no travel page can give you a current answer. Medicines that are unremarkable in the United States are controlled or banned in some countries, including certain stimulants, painkillers and even some over-the-counter cold remedies. Carry everything in the original labeled containers, carry a written list of generic names and doses, and ask your prescriber for a letter if you take anything unusual. The authoritative source is the destination country's embassy or health ministry, checked before you book anything you cannot cancel.