Efficient use of spectrum requires an accurate determination of interference effects. In this paper, we introduce a Radio to Radio (R2R) factor that quantifies the interference effects of one radio waveform on another based on multiple waveform properties instead of solely on intermediate frequency (IF) signal power. The R2R factor is formulated as a dimensionless correction term in the victims communication link budget. The factor provides an effective interference margin in the link budget, taking into account modulation schemes, frequency offset, and power offsets of the intended source of communication ("victim") and the interferer. For a specified set of modulation parameters we simulate a scenario where the victim signal is interfered by the interferer signal. The interfered victim signal is then demodulated by the intended receiver in the presence of additive white Gaussian noise (AWGN). The sent and received data streams are compared to determine a bit error rate (BER) induced by the interference. This BER is then mapped to an effective signal to noise and interference ratio that produces the same BER in an AWGN channel. The R2R factor is then the difference between this effective signal to noise and interference ratio and the actual signal to noise and interference ratio of the communication link. In this paper we demonstrate how the R2R factor may be computed, and show examples for several cases of victim and interferer modulations.