How this calculator works
Absorbed dose measures the energy deposited per unit mass of material. Its SI unit is the gray, one joule per kilogram, and the older unit is the rad, with 1 rad exactly 0.01 Gy. Equivalent dose measures the biological effect of that energy, weighting different radiation types. Its SI unit is the sievert, and the older unit is the rem, with 1 rem exactly 0.01 Sv. The two families are not interchangeable without a radiation weighting factor, which depends on the type of radiation, so this page never mixes them. The banana equivalent dose is an informal teaching unit of about 0.1 microsievert.
Formula
grays = value x F(absorbed unit), where F is 1 for Gy, 0.001 for mGy, 0.01 for cGy, 10^-9 for nGy and 0.01 for rad. sieverts = value x F(equivalent unit), where F is 1 for Sv, 0.001 for mSv, 10^-6 for µSv, 0.01 for rem, 10^-5 for mrem and 10^-7 for one banana equivalent dose. Convert within a family by dividing by the target factor.
Worked example
1 Gy is 100 rad, 1,000 mGy and 1,000,000,000 nGy. 1 Sv is 100 rem or 1,000 mSv. 1 mSv is 0.1 rem or 10,000 banana equivalent doses. 1 cGy is 10 mGy.
Advertisement
Frequently asked questions
Are gray and sievert the same?
They have the same dimensions and the same SI size, but they describe different quantities. The gray is physical absorbed energy per mass. The sievert is a weighted biological equivalent, so 1 Gy of alpha radiation can correspond to many sieverts while 1 Gy of X-rays corresponds to about 1 Sv.
How do rad and rem relate to gray and sievert?
One rad is exactly 0.01 gray, and one rem is exactly 0.01 sievert. The older units remain in some regulations and instruments, so 100 rad is 1 Gy and 100 rem is 1 Sv.
What is a banana equivalent dose?
It is an informal unit based on the tiny amount of radioactive potassium-40 in a banana, roughly 0.1 microsievert. It is useful for scale, not for regulation or medical decisions.