The 3-1-1 rule applies only to carry-on baggage. In a checked bag you can pack full-size toiletries freely. That is the headline difference, and it is why the choice of bag changes what you pack.
The comparison
| Carry-on | Checked | |
|---|---|---|
| Max container size | 3.4 fl oz (100 ml) | Effectively unlimited for toiletries |
| Must fit a quart bag | Yes | No |
| Aerosols | Yes, within 3.4 oz | Yes, with quantity limits |
| Flammables (some nail products) | Restricted | Restricted |
| Risk of loss or delay | None | Real |
| Cost | Usually included | Often $35–$75 |
What is still restricted in checked bags
"No limit" is not quite true. Checked baggage still restricts:
- Aerosols — toiletry aerosols are allowed but capped in total quantity, and caps must be protected against accidental release
- Flammable liquids — including some nail polish removers and certain hair products
- Anything explicitly forbidden — lighter fuel, large lithium batteries and similar
For ordinary shampoo, conditioner, body wash and lotion, none of this applies.
Why people still pack small when checking a bag
Three reasons, all sound:
- Weight. Liquids are heavy. Four full-size bottles is well over a kilogram of allowance spent on shampoo.
- Leaks. Checked bags are handled roughly and experience the same pressure changes. A full-size bottle bursting ruins considerably more.
- Your bag might not arrive. If toiletries are all checked and the bag is delayed, your first night is a shopping trip.
A sensible habit even when checking: keep a minimal set in the carry-on regardless, so a delayed bag is an inconvenience rather than a problem.
The honest cost comparison
Checking a bag purely to carry full-size toiletries rarely makes sense. One round-trip checked bag fee typically exceeds the cost of a complete travel kit that you will reuse for years.
Our Ultimate Travel Kit is $16.99 for four products — less than half a single checked bag fee on most airlines, and it ships free.
International differences
Most countries follow the same 100 ml standard, though the bag is often specified as one litre rather than one quart. They are close enough that a compliant quart bag will pass almost anywhere. Some airports have installed newer scanners that relax the rules, but enforcement is inconsistent — pack to the 100 ml standard and you will never be caught out.