A fly hitting a train

Maybe, I'm not much of a physicist. Most of the websites I found insisted on talking about electrons and protons as waves instead of particles. It probably makes more sense. There were a few that talked about them as particles and none of them agreed on a physical size. 10^-25 seemed like the middle of the pack of the estimates but that doesn't make it correct.

 

I don't think anybody has a really good estimate of the size of a proton. At the atomic level, quantum mechanics takes over and everything becomes fairly fuzzy. Heisenberg uncertainty becomes very significant, and everything is wavelike.

Entire atoms are roughly 10^-10 m in diameter, though even at that level things are somewhat fuzzy. An atomic nucleus is of the order of 10^-15 m in diameter. Go smaller than that and the quantum description takes over more or less completely. The quarks making up a proton, for example, are more of a collective jumble than individually identifiable particles. As far an anybody can tell, leptons such as electrons have essentially no measurable diameter - they can be considered as point particles in terms of size, but that is not usually an important feature, since they interact primarily via their electromagnetic effects, under most conditions.