A method has been presented for accounting for ion fragmentation that occurs within the nonzero field of an ionic electrospray thruster. Given the complexities associated with direct thrust measurements, indirect means (and time-of-flight (TOF) in particular) remain a primary method for researchers to evaluate performance. The described method applies to measurements made with Faraday cup type detectors and requires an assumption as to the specific fragmentation events that occur, yet it is otherwise easily applied through modifiers to the integrands used to calculate thrust and mass flow rate from TOF traces. Energy-resolved TOF measurements could segregate contributions and provide improved fidelity but may be convoluted by further fragmentation within the filtering instruments and add system complexity when compared with this analytical approach.