TSA 3-1-1 Rule Calculator
| Rule part | Requirement |
|---|---|
| Container size | 3.4 oz (100 ml) or less per item |
| The bag | One quart-sized, clear, resealable bag |
| Per traveler | One bag only, separated at screening |
| Oversize containers | Checked baggage |
| Exempt | Medications, baby formula, breast milk — declare at screening |
Rule: TSA, Liquids Rule (3-1-1) — liquids, aerosols, gels, creams and pastes in 3.4 oz (100 ml) or smaller containers; the two figures are both accepted though not identical (3.4 fl oz = 100.55 ml). Liquid or gel FOOD over 3.4 oz goes in checked bags per TSA's What Can I Bring list. Anything that alarms gets extra screening regardless of size. Related: carry-on size calculator, passport processing time calculator, holiday shipping calculator.
The TSA liquids rule is four words deep and a hundred arguments wide: 3.4 ounces per container, one quart bag per traveler. But the security line where you are standing accepts 100 milliliters too — and those are not the same number. A 100 ml bottle is 3.38 fluid ounces, inside the 3.4 limit; a 3.4 oz bottle is 100.55 ml, technically over the metric figure. TSA accepts either standard, which is why a European 100 ml perfume and an American 3.4 oz spray both clear the same checkpoint.
Enter a container size and this calculator gives the verdict in both units — plus the rest of the rule the number sits inside: the bag is quart-sized, clear and resealable; there is exactly one bag per passenger; and anything bigger goes in a checked bag, along with liquid and gel FOOD items, which follow the same 3.4-ounce line in carry-ons.
How to use
- Enter the container size and pick the unit printed on the bottle — fl oz for American labels, ml for everything else.
- Read the verdict: carry-on legal, or checked bag only if the container exceeds both limits.
- Count your containers against the bag: one quart-sized, clear, resealable bag per traveler, liquids separated from the carry-on at screening.
Frequently asked questions
Is 3.4 ounces the same as 100 milliliters?
Almost but not exactly: 3.4 fl oz is 100.55 ml, and 100 ml is 3.38 fl oz. TSA accepts either figure — a bottle labeled 100 ml passes even though it is a hair under 3.4 oz, and a 3.4 oz bottle passes even though it is a hair over 100 ml. The two standards coexist on purpose so both labeling systems work.
Does the quart bag have to be a Ziploc?
No brand requirement — it must be quart-sized, clear and resealable. A store-brand zip bag passes as long as it is actually a quart (about 7 by 8 inches); a larger gallon bag does not, and an opaque pouch defeats the point of the rule, which is fast visual screening.
Can I bring soup, gravy or jam through security?
Only in containers of 3.4 ounces or less — TSA's own guidance says liquid or gel food items larger than 3.4 oz are not allowed in carry-ons and should go in checked bags. Solid food travels fine; the line is whether you can pour, spread or squeeze it.
Do medications and baby formula count against the limit?
No — prescription and over-the-counter medications, baby formula, breast milk and juice for toddlers are exempt from the 3.4-ounce limit in reasonable quantities. Declare them at screening and expect them to be opened or tested; the exemption is not a secrecy pass.
What about duty-free liquids on a connecting flight?
Duty-free purchases come sealed in a STEB — a security tamper-evident bag with the receipt inside. That seal keeps them carry-on legal between flights; break the seal mid-journey and the 3.4-ounce rule applies again at the next checkpoint.