About RxMath Lab
Who makes this, how the problems are generated, and what has and has not been checked.
RxMath Lab is a free, unlimited pharmacy calculation practice generator. There is no sign-up, no question limit, no paywall and no advertising. It exists because the calculation question banks available to students are finite, and running out of fresh problems two weeks before an exam is a bad place to be.
Who writes it
It is written and maintained by one person: Arman Kiledjian, PharmD, in California. He holds the Doctor of Pharmacy degree and is preparing for the NAPLEX and the CPJE; he is not yet licensed, so he is not an RPh and nothing here is written in the capacity of a licensed pharmacist. The license number will be added to this page once boards are behind him.
Nobody is paid, nothing is sponsored, and no company has any input into the content. There are no affiliate links. If that ever changes it will be disclosed on this page before it changes anywhere else.
How the problems are made
Every problem is generated by code, not written by a language model and not copied from a question bank. A generator for each topic picks the clinical variables — a patient weight, a vial strength, a set drop factor, an infusion rate — from ranges chosen to be realistic, then computes the answer from the same formula that is printed in the worked solution. The question and its answer come from one calculation, so they cannot disagree with each other.
This is the reason the arithmetic can be trusted even though the volume is unlimited: there is no answer key to fall out of sync with the questions, because there is no answer key. The step-by-step solution shown when you press Show steps is generated from the same numbers, in the same pass.
Rounding is handled explicitly rather than left to chance. Every question states the rounding it expects before you answer — two decimal places, a whole number, round up — and grading enforces exactly that. Where a quantity is physically indivisible, such as a count of vials or bottles, the answer rounds up even when the arithmetic would round down, because a fraction of a vial is not something a pharmacy can dispense.
What is actually verified
Five automated test suites run before every deployment. They check that the answer printed on the page is the answer the grader accepts; that the browser and the build produce identical problems from identical inputs; that the rounding instruction shown to you is the rounding actually enforced; that the pre-rendered worked solutions match what the live tool generates; and that no page ships with a broken link, a missing heading, or a layout that shifts as it loads.
What is not verified — read this part
Those suites check that the site is internally consistent. None of them checks that the pharmacy is correct. If a formula on this site were wrong, every test would still pass, and would simply confirm that the site is consistently wrong.
The formulas were written by one person who holds the degree but not yet the license, and no second person has independently reviewed them. One author checking their own work is the weakest link on this site, and no amount of testing changes that. Each topic page names the standard, textbook or labeling its method comes from so you can check it yourself, and you should — particularly before relying on anything here for an exam. If you find an error, please report it to [email protected]; corrections are made quickly and are the most useful thing anyone can send.
Not for clinical use
This is exam preparation and educational material. It is not a clinical decision tool, and nothing on it should be used for patient care, dosing, or dispensing. Real practice requires current primary references, the specific product's labeling, and your own professional judgement.
Contact
Corrections, questions, and requests for topics that are not covered yet: [email protected]. Every message is read.