One frustration that persists in making judgements about technical matters is that it has not yet been possible to develop a consistent system of units. People are creatures of habit and tend to use those units with which they are familiar. Old and useful textbooks and reference materials use old units that are out of fashion. Many millions of hours have been spent in engineering and science classes converting from English to Metric or from “old” International System of Units (SI) to “new” SI units.
It is irritating to need to refer to a book of conversion factors with a calculator handy just to obtain useful information. We regret that we have no solution to the problem in a global sense, but when we use numbers in this letter we will attempt to consistently use modern SI units.
We will include tables to help people familiar with other systems to be able to use the numbers.
For this issue, the following table may be helpful.
| quantity measured | old unit | symbol | new unit | symbol | relationship |
| Dose | rad | rad | gray | Gy | 1 rad = .01 Gy 100 rad = 1 Gy |
| Dose equivalent | rem | rem | sievert | Sv | 1 rem = .01 Sv 100 rem = 1 Sv |
| Radioactivity | curie | Ci | becquerel | Bq | 1 Ci = 3.7e10 Bq 1 pCi/l = 37 Bq/m3 |
