Radiation Converter (Absorbed Dose)

The Radiation Absorbed Dose Converter converts between units of absorbed radiation dose and dose equivalent. It covers both absorbed dose (energy deposited per unit mass: gray/rad) and dose equivalent (biological effect: sievert/rem).

The gray (Gy) is the SI unit of absorbed dose, defined as one joule per kilogram of material. The older unit is the rad (radiation absorbed dose), where 1 rad = 0.01 Gy = 10 mGy. The gray measures the physical energy deposition regardless of radiation type or biological effect.

The sievert (Sv) is the SI unit of dose equivalent, accounting for the biological effectiveness of different radiation types. For gamma rays and beta particles, 1 Sv = 1 Gy (radiation weighting factor = 1). For alpha particles, 1 Sv = 0.05 Gy (weighting factor = 20), because alpha particles cause 20 times more biological damage per gray. The older unit is the rem, where 1 rem = 0.01 Sv.

Note: This converter treats Gy and Sv as numerically equivalent (appropriate for gamma/beta radiation). For alpha or neutron radiation, a radiation weighting factor must be applied separately to convert between Gy and Sv.

Radiation dose context: average annual background dose is about 2.4 mSv (240 mrem). A chest X-ray delivers about 0.02 mSv (2 mrem). A CT scan delivers 1–20 mSv. Cancer radiation therapy delivers 20–80 Gy to tumors over multiple sessions.