Sievert (SI unit)

Last revised by Andrew Murphy on 29 Mar 2020

The sievert (symbol Sv) is the SI unit of dose equivalent and is dimensionally-equivalent to one joule per kilogram. The sievert represents the stochastic effects of ionizing radiation as adjusted by a tissue weighting factor to account for differing responses of different human tissues to ionizing radiation and the differing effects of different forms and energies of this radiation.


One sievert is a large unit and is usually used with a prefix, e.g. millisievert (mSv) or microsievert (μSv).

As per all other eponymous SI units when the unit is written out in full it is not capitalized, but when shortened to its symbol it is capitalized.

History and etymology

The sievert was adopted as the official SI unit at the 16th General Conference of Weights and Measures (CPGM) in 1979 2.

The sievert replaced the old unit, the rem.

The unit is named after the Swedish physicist Rolf Maximilian Sievert (1896-1966), who made major contributions to the understanding of the biological effects of ionizing radiation 3.

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