The radioactivity of a given material is a measure of the rate at which the material undergoes radioactive decay.

The unit used to measure radioactivity is the curie (Ci) where one curie equals 3.7 x 10¹⁰ radioactive disintegrations per second (dps).

The SI unit which may be used in place of the curie is the becquerel (Bq).

These units are related as follows:

1 Ci = 3.7 x 10¹⁰ dps = 3.7 x 10¹⁰ Bq

1 Bq = 1 dps