Original: The diameter of the nucleus is in the range of 1.6 fm (for a proton in light hydrogen) to about 15 fm (for the heaviest atoms, such as uranium).
Simplified: The size (diameter) of the nucleus is in the range of 1.6 fm (10-15 m) (for a proton in light hydrogen) to about 15 fm (for the heaviest atoms, such as uranium).