Individual fullerene nanoparticles are detected and sized in a non-aqueous solution via cathodic particle coulometry where the direct, quantitative reduction of single nanoparticles is achieved upon collision with a potentiostated gold electrode. This is the first time that the nanoparticle impact technique has been shown to work in a non-aqueous electrolyte and utilized to coulometrically size carbonaceous nanoparticles. Contrast is drawn between single-nanoparticle electrochemistry and that seen using nanoparticle ensembles via modified electrodes.