In a method for forming nanopores, two opposing surfaces of a membrane are exposed to an electrically conducting liquid environment. A nanopore nucleation voltage pulse, having a first nucleation pulse amplitude and duration, is applied between the two membrane surfaces, through the liquid environment. After applying the nanopore nucleation voltage pulse, the electrical conductance of the membrane is measured and compared to a first prespecified electrical conductance. Then at least one additional nanopore nucleation voltage pulse is applied between the two membrane surfaces, through the liquid environment, if the measured electrical conductance is no greater than the first prespecified electrical conductance. At least one nanopore diameter tuning voltage pulse, having a tuning pulse voltage amplitude and duration, is applied between the two membrane surfaces, through the liquid environment, if the measured electrical conductance is greater than the first prespecified electrical conductance and no greater than a second prespecified electrical conductance.