5 nanometers.
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A 12-inch wafer is not necessarily related to a few nanometers. The 12-inch wafer is the main material for making chips, and the 12-inch silicon-based wafer is 300 mm in diameter, and the ultra-large scale integrated circuit is carved on it by the lithography machine. The process of engraving chips can be as small as 3 nanometers, and as large as tens of hundreds of nanometers. The exact number of nanometers depends on what type of chip the manufacturer makes. For example, the mainstream high-end mobile phone 5-nanometer chip, with a 12-inch wafer, each piece can be carved into about 500 chips.