What is the size of a proton (in nm)?

The size of a proton is approximately 0.84 to 0.87 femtometers (fm), which is equivalent to 0.00084 to 0.00087 nanometers (nm). This makes protons incredibly small, about 100,000 times smaller than a typical atom. However, due to their quantum properties, protons do not have a definite boundary, and their effective size can depend on the context in which they are being measured.