Calculations of the transmutation of pure copper have been performed for the Fast Flux Test Facility/Materials Open Test Assembly (FFTF/MOTA) and for the STARFIRE first-wall fusion reactor. The principal transmutation products in decreasing order of importance are nickel, zinc, and cobalt. Contrary to previously published calculations, nickel and zinc are produced at nearly equal rates in FFTF, but cobalt is insignificant. The fusion reactor case shows much higher transmutation rates and produces about twice as much nickel as zinc. Transmutation rates for FFTF were determined using adjusted neutron energy spectra based on dosimetry measurements at various positions in the MOTA. The predicted transmutation rates were compared directly with nickel concentrations measured by Energy Dispersive X-Ray Spectrometry (EDS) microchemistry and with measurements of the electrical conductivity of copper and two copper alloys irradiated in the MOTA. Measurements and calculations agree within ±15%.