Sievert

The Sievert (Sv) is the SI unit of equivalent radiation dose, representing absorbed radiation energy weighted by how biologically damaging that specific type of radiation is. It's the standard unit used internationally for medical imaging dose reports, occupational radiation safety limits, and environmental radiation monitoring outside the United States.

The Radiation Dose Converter converts sievert to and from gray, rad, and the older rem unit still commonly used in the US.

1 Sievert = 100 rem 1 Sievert = 1,000 millisievert (mSv) 1 Gray (absorbed dose) ≈ 1 Sievert (for radiation types with a weighting factor of 1: X-rays, gamma rays, beta particles)

Converting 5 mSv (a typical annual medical imaging dose) to millirem:

Result = 5 × 100 = 500 millirem

This confirms the standard 100:1 relationship between millisievert and millirem.

• SI standard for radiation dose: sievert is the internationally recognised unit, while the US commonly uses rem for occupational and some medical reporting.
• Distinct from gray: gray measures raw absorbed energy; sievert weights that energy by biological damage potential, though they're numerically equal for the most common radiation types.
• Reference points help with scale: a chest X-ray (~0.1 mSv) and annual background radiation (2–3 mSv) provide useful context for interpreting any dose value.
• 100:1 conversion to rem: this fixed factor makes conversion between US and international dose reporting straightforward once you know the direction.