Pharmacists and pharmacy technicians use a mathematical system called pharmacy math (sometimes called the apothecaries’ system). While the metric system has units for volume, length and weight, pharmacy math uses only weight (measured in grains) and volume (measured in minims). While the metric system is quickly taking over as the dominant force in medicine, pharmacists and pharmacy technicians must be able to read and convert prescription orders, which are sometimes still written in pharmacy math.
Check the required reading list for pharmacy classes at a local college. The information is public and the books are even available right in the bookstore on campus. These books will be the most up to date, as they are being taught currently.
Contact a pharmacist in your area to ask about how they use pharmacy math, and where they learned it from. Their information should be good since they are practicing, but could be a little out of date because they haven’t been in school for some time.
Visit a library to check out pharmacy books. The books you find will almost certainly be seminal books in the field but may not be modern enough to give you a sense of how pharmacy math is used in practice.
Enroll in a math for pharmacy technicians class. Many community colleges offer such courses, and you may not need to be part of their degree program to enroll.
Most libraries have access to a wide array of book collections, so if you can’t find the books you’re looking for at the branch you visit, ask a librarian and you may be able to have it shipped to you.