The mass resolving power (MRP) in APT is generally defined as m/∆m, where ∆m is measured as the full-width at half-maximum (FWHM) of the peak. MRP is typically up to 500 for voltage-pulsed atom probes and up to 1000 for laser-pulsed atom probes. It can reach more than 2000 with laser-assisted reflectron-equipped instruments.

The mass resolution is dependent on many factors such as voltage pulse fraction or laser energy, pulse frequency, temperature, thermal and electrical conductivity of the specimen and the geometry of the tip. Optimisation of the mass resolution requires testing the experimental conditions for each sample type.