Three dosimetric quantities
The calculator converts dose units within three distinct dosimetric quantities. Equivalent dose is measured in sievert (Sv, mSv, µSv) and rem (rem, mrem): 1 Sv = 100 rem. Absorbed dose is measured in gray (Gy, mGy, µGy) and rad (rad, mrad): 1 Gy = 100 rad. Exposure dose is expressed in roentgen (R, mR).
Cross-conversion between families
Within one family the conversion is exact, by fixed factors. Between families (gray → sievert, roentgen → sievert or gray) it works only with explicit context: the radiation type sets the weighting factor w_R in Sv = Gy × w_R, and for roentgen the medium (air, tissue, water) sets the step Gy = R × medium factor. You set these assumptions yourself — the calculator shows the coefficient, the formula and the standard (NRB-99/2009 or ICRP-103), and marks the cross result as an estimate.
Equivalent vs effective dose
Absorbed, equivalent and exposure dose are kept strictly distinct here. A cross conversion returns equivalent dose H = D · w_R, not effective dose, which needs organ tissue weighting factors. The value of w_R depends on the standard — for protons and neutrons NRB-99/2009 (legal in Russia) and ICRP-103 diverge, so the standard is switched in the calculator.
Frequently asked questions
How many roentgens are in a sievert?
For gamma radiation in soft tissue 1 Sv ≈ 104 R and 1 R ≈ 0.0096 Sv; in air 1 R = 0.00876 Gy. The exact factor depends on the medium and radiation type — the converter lets you choose both explicitly.
What is the difference between sievert, gray and roentgen?
The gray is absorbed dose (J/kg), the sievert is equivalent or effective dose weighted by the radiation weighting factor, and the roentgen is exposure in air for photons. For photons and beta w_R = 1, for alpha it is 20.
How do I convert rem to sievert?
1 rem = 0.01 Sv (1 Sv = 100 rem) and 1 rad = 0.01 Gy. These are exact relations between the older non-SI units and the modern SI units.
