A memory controller identifies a predominant type of error of a memory unit of solid state memory cells. An error type differential is calculated. The error type differential is a difference between a number of charge loss errors and a number of charge gain errors of the memory unit. A VT offset error differential is calculated. The VT offset error differential is a difference between a number of errors of the predominant type at a first VT offset and a number of errors of the predominant type at a second VT offset. A VT offset is determined using a ratio of the error type differential and the VT offset error differential.