The TSA’s "3.4-ounce" limit is the cornerstone of the 3-1-1 rule for carry-on liquids, and in metric terms, it is exactly 100 milliliters (100ml). To visualize this, 3.4 ounces is roughly equivalent to 7 tablespoons of liquid. This is about the size of a standard "travel-size" shampoo bottle or a small tube of toothpaste. It is important to note that the TSA measures the container size, not the amount of liquid inside; for example, a 6-ounce bottle that is only a quarter full will still be confiscated because the container exceeds the 3.4-oz limit. All of your 3.4-oz (100ml) containers must fit comfortably inside a single one-quart, clear, zip-top plastic bag. In 2026, while some airports are deploying advanced scanners that may eventually allow larger liquids, the 100ml rule remains the international standard. For perspective, a standard soda can is 12 ounces, meaning the TSA limit is less than a third of a can of Coke.