I can calculate the number of electrons striking the annode in an X-ray tube. I read here that the electrons convert 1% of their energy to x-ray photons. So I thought that the most straightforward way to estimate the radiation dose would be to think about the number of X-ray photons and then think about what percentage of those photons would cause an ionization in air or body tissue. I don't know what the standard way to do this is. I have read about the doses from X-ray machines and I am wondering how they were found.

Yes I was referring to the number of photons