To calculate the number of protons and neutrons in an atom, one needs to know the atomic number and mass number of the atom. The number of protons in an atom is the same as the atomic number. The mass number, on the other hand, is a sum total of the number of protons and neutrons.
Hydrogen has 3 common isotopes (atoms that have the same atomic number but different mass numbers): protium, deuterium, and tritium. All these isotopes have an atomic number of 1, but the mass numbers of these isotopes are 1, 2, and 3, respectively.
This means that all these isotopes have only 1 proton (since the atomic number is 1). However, protium has 0 neutrons (mass number - atomic number=1-1=0), deuterium has 1 neutron (2-1=1), and tritium has 2 neutrons (3-1=2) in it.