Background: The total yields of direct Single-Strand Breaks (SSBs) and Double-Strand Breaks (DSBs) in proton energies varying from 0. 1 to 40 MeV were calculated. While other studies in this field have not used protons with energy less than 0. 5 MeV, our results show interesting and complicated behavior of these protons. Materials and Methods: The simulation has been done using the Geant4-DNA toolkit. An atomic model of DNA geometry was simulated. Simulations were performed with a source in the Z-axis direction at the cell nucleus entrance with protons at energies of 0. 1-1 MeV in 0. 1 MeV steps, 5 MeV, and 10-40 MeV in 10 MeV steps. Results: The calculated SSB yields decreased from 60. 08 (GbpGy)− 1 for 0. 1 MeV proton energy to 49. 52 (GbpGy) − 1 for 0. 5 MeV proton energy, and then it increased to 54. 35 (GbpGy)− 1 in 40 MeV. The DSB yields decreased from 4. 32 (GbpGy)− 1 for 0. 1 MeV proton energy to 1. 03 (GbpGy)− 1 for 40-MeV protons. The DSB yields for energies less than 0. 5 MeV was about 56%, and for the other energy levels, it was 44%. As for SSB yields, 35% of the breaks arose from protons with an energy of fewer than 0. 5 MeV and 65% from higher energies. Conclusion: It was found that the proton ranges with an energy less than 0. 5 MeV are smaller than the cell size (10 μ m), and 100% of the energy is deposited in the cell region. Then protons with these energies are the best choice to increase the number of DSBs.