Radiation Dose Converter (Gy, Sv, rad, rem)

How it works

1 Gy = 100 rad = 1 J/kg (absorbed dose D) · 1 Sv = 100 rem (equivalent dose H) · H = wR × D · wR: photons and electrons 1, protons 2, alpha particles 20, neutrons 2.5–20.7 depending on energy (ICRP 103)

Absorbed dose (gray, or the older rad) is the energy deposited per kilogram of tissue. Equivalent dose (sievert, or rem) weights it by how damaging the radiation is: for X-rays and gamma rays 1 Gy gives 1 Sv, but alpha particles are weighted 20 times. Effective dose, which also weights each organ by its sensitivity, uses the same sievert unit but needs the whole exposure pattern. The weighting factors are the ICRP Publication 103 values; this is a unit converter, not a dosimetry or medical tool.

Worked example

A dose of 1 rem from X-rays or gamma rays (wR = 1) equals 0.01 Sv, which is 10.00 mSv of equivalent dose. Because wR = 1, the absorbed dose is 10.00 mGy (1 rad). That is about 4.17 times the world-average yearly natural background of 2.4 mSv.

Sources: ICRP Publication 103 (2007 Recommendations) · US NRC — Measuring radiation · UNSCEAR — Sources and effects of ionizing radiation

Frequently asked questions