The Sievert (Sv) is the unit (SI-unit) of dose equivalent and effective dose. In general, fractions of the unit of dose are used in radiation protection practice: 1 Sievert = 1 000 millisieverts (mSv) = 1 000 000 microsieverts (µSv) = 1 000 000 000 nanosieverts (nSv).

Dose is often related to a period of time, i.e. per year (mSv/a) or per hour (mSv/h).