A 28-nanometer chip is about 400 square millimeters.
A typical 14-nanometer cpu chip is about 160 square millimeters when unpackaged, which is about the size of a fingernail. The 28-nanometer chip is currently not suitable for mainstream computers, mainly used in vehicles, ships, aircraft and other electronic devices with low space requirements, and 400 square millimeters is about a little more than six centimeters long.
A 28nm chip is about 400 square millimeters.