A method for determining a monitor unit that is associated with a process using ions, includes obtaining a depth dose curve, determining a characteristic parameter based on the depth dose curve, and using the characteristic parameter to determine a first monitor unit factor. A system for determining a monitor unit that is associated with a process using protons, includes a processor that is configured for obtaining a depth dose curve, determining a characteristic parameter based on the depth dose curve, and using the characteristic parameter to determine a first monitor unit factor.