What the trip type changes
The type you pick swaps whole blocks of the list in and out. A domestic weekend drops the passport, the plug adapter and the luggage scale, and stays short. International adds passport, visa, insurance and photocopies, plus a lock and a scale for the flight home. Camping replaces most of that with tent, sleeping gear, cook set and trash bags. Business adds a laptop, cards and meeting materials. Traveling with children widens the clothing counts, adds diapers and a thermometer, and puts the familiar toy on the list, which sounds soft and is the difference between a good night and a bad one.
Weather changes the clothing block on top of that. Hot adds a light layer for over-air-conditioned rooms, a hat and sandals. Cold adds a coat, base layers and gloves. Wet adds a rain shell, quick-drying shoes and extra socks, which is the single highest-value line on any list for a wet trip.
Where the counts come from
Underwear and socks are set at one more than the number of days. The extra covers the journey home and the delay nobody planned for, and both items are small enough that carrying a spare costs nothing. Past ten days the count stops climbing, because nobody packs eighteen pairs of underwear; from there the list assumes you will wash something, and says so.
Tops run at one per two days plus one, capped at eight. Bottoms run at one per three days plus one, capped at five. Both are conventions rather than measurements, and they are the first numbers to override. Somewhere hot, tops go to one a day. Somewhere with a washing machine, halve everything and bring detergent instead. For children, the counts are doubled and still routinely too low.
Reading the bag rule column
Four flags appear. Liquids rule means the item is subject to the container size limit in a carry-on: 3.4 oz or 100 mL per container, everything in one quart-size clear bag. The limit goes by the size printed on the container rather than the amount inside, which is why a nearly empty large bottle still gets taken. Carry-on only is the reverse: power banks and spare lithium batteries are barred from the hold and have to be with you. Checked bag covers blades and long rigid items that will not get through the checkpoint. Not allowed means neither bag will take it, which for most people is camp stove fuel.
All of that describes how screening generally works and is written from the US case. The actual rules are set by the security authority of the country you are departing from and by your airline, they are not identical between countries, and they get revised. Duty-free liquids bought after security are handled differently again, and a connection in a third country can undo that exemption. The list flags what usually causes trouble; it is not the authority on any of it, and a five-minute check on your airline's site before you pack is worth more than any of the above.
Medication is the one to get right
Prescription medication goes in the carry-on, in the original labelled container, with enough for the trip plus a few days. A checked bag that ends up in another city is an inconvenience for clothes and a genuine problem for anything you take daily. Medically necessary liquids are usually exempt from the container limit but generally need to be declared at the checkpoint rather than hidden in the quart bag. Rules on carrying specific medications across borders vary considerably and some ordinary prescriptions are controlled elsewhere, so for international travel that is worth checking against the destination country's own guidance.
Use it as a draft
Nothing here is a finished list, and it is not meant to be. Delete the towel if the hotel has towels, delete half the toiletries if you are staying with family, and add the things you personally always bring to the additions box, with a count after a pipe if the count matters. Then print it. The sheet has a box for packing and a second box for repacking on the last morning, which exists because the items people leave in hotel rooms are overwhelmingly chargers and things in the bathroom, and both are on this list.
Questions people ask
Why one more pair of underwear than days?
The day you travel home still needs a clean set, and trips run long often enough to be worth planning for: a cancelled flight, a missed connection, a night added at the end. Underwear and socks are the cheapest possible insurance in terms of space and weight, which is why the rule of thumb has survived. The counterargument is real too. If there is a washing machine where you are staying, three days worth plus a small bottle of detergent beats packing for the whole trip, and it makes a genuine difference to the size of the bag on a two-week trip.
What do I do about liquids over the size limit in a carry-on?
Three options. Put them in a checked bag, where the container limit does not apply. Decant into travel-size containers before you leave, which is what the limit is designed to accommodate. Or switch format: solid shampoo bars, toothpaste tablets and sheet detergent all exist to sidestep this exact problem. Duty-free liquids bought after security are treated separately and can usually come aboard sealed in the tamper-evident bag with the receipt, but a connecting flight that re-screens you in another country can break that, so check the whole itinerary rather than just the first leg.
Can I use this for a road trip where nothing flies?
Yes, and the bag rule column simply stops applying. Pick camping or road trip as the type and the list swaps to gear rather than documents. The fuel canister flag is the only line that becomes irrelevant, and it says as much in the warnings when you choose that trip type. Everything else — the clothing counts, the toiletries, the medicine kit — works the same way regardless of how you get there.
Does the list save so I can use it again next trip?
No. It is generated fresh in your browser each time and nothing is stored or uploaded. The practical approach is to copy the text output into a notes app once, edit it down to the version that actually matches how you travel, and keep that. After two or three trips your own edited list beats any generated one, and this tool becomes the thing you check it against rather than the thing you use.