There are 33.81 ounces in a liter, but on most containers it is rounded off to an even 32 ounces. A liter is actually a metric measurement, but is commonly used in the United States for measuring liquids.
There are two spellings for this measurement, the American spelling of liter and the spelling recognized by the International Bureau of Weights and Measures, which is litre. This unit of measure is not listed as part of the International System of Units, abbreviated as SI, but is mentioned in the listings because it is commonly used worldwide. The liter actually started out as the base unit for the French metric system.