The amount of deodorant you can take on a plane depends entirely on its physical form: solid sticks are unrestricted, while liquids, gels, and sprays must follow the 3-1-1 rule. If your deodorant is a solid stick, there is no size limit; you can pack a full-size 75ml or 100ml stick in your carry-on without any issues. However, if you use spray (aerosol), gel, roll-on, or cream deodorant, it is classified as a liquid by the TSA and most international aviation authorities. In these cases, the container must be 100ml (3.4 ounces) or less. Even if a 150ml spray can is nearly empty, security will likely confiscate it because the limit applies to the container capacity, not the remaining volume. All these "liquid" deodorants must fit inside a single quart-sized (approx. 1 liter) clear, resealable plastic bag along with your other toiletries. If you need to bring a large can of spray or a big tub of gel, you must pack it in your checked luggage, where aerosols are permitted up to certain limits (usually 500ml per container and 2L total per person).