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Radiation Conversion Table

International System of Units (SI)

International System (SI) metric radiation units are used throughout the world. The United States was in a transition period until 1 April 1996 when the U. S. Department of Transportation mandated the exclusive use of SI units on labels and placards. Below is a comparison of radiation units used.

Former Units SI Units
1 curie (ci) = 37 billion Becquerel (Bq)
1 Roentgen (R) = 2.58 X 10-4 coulomb per kg of air
1 rad = .01 Gray (Gy)
1 rem = .01 Sievert (Sv)


Equivalents For Conversion

Quantity (Activity)

1 TBq = 27 Ci = 27,000 mCi
1 GBq = 0.027 Ci = 27 mCi = 27,000 uCi
1 MBq = 0.000027 Ci = 0.027 mCi = 27 uCi
1 Ci = 0.037 TBq = 37 GBq = 37,000 MBq
1 mCi = 0.000037 TBq = 37 MBq
1 uCi = 0.037 MBq = 37,000 Bq
1 nCi = 0.000037 MBq = 37 Bq
1 pCi = 0.037 Bq = 37 mBq


Radiation Level (Dose Equivalent Rate)

1 Sv/h = 100 rem/h = 100,000 mrem/h 1 mSv/h = 0.1 rem/h = 100 mrem/h
1uSv/h = 0.0001 rem/h = 0.1 mrem/h
1 rem/h = 0.01 Sv/h = 10 mSv/h = 10,000 uSv/h
1mrem/h = 0.00001 Sv/h = 0.01 mSv/h = 10 uSv/h

To convert a value from the "Customary System of Units" to SI units and vice versa, use the following directions:

Step 1: On the left side, find the unit you want to convert FROM.
Step 2: Find the factor in that line for the unit you want to convert TO.
Step 3: Multiply the original value by the factor, and the result will be the
measure in the desired units.

Example: Say a package has 20 TBq of radioactive material. How many curies does this correspond to?

Answer: Following Step 1, we immediately find 1 TBq = 27 Ci
Following Step 2, we find that the "factor" is 27 Ci
Following Step 3, we multiply 20 x 27 which = 540
Answer is: 540 Ci