count rates of cps and cpm are generally accepted and convenient practical rate measurements. They are not SI units, but are de facto radiological units of measure in widespread use.

Counts per minute (abbreviated to cpm) is a measure of the detection rate of ionization events per minute. Counts are only manifested in the reading of the measuring instrument, and are not an absolute measure of the strength of the source of radiation. Whilst an instrument will display a rate of cpm, it does not have to detect