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. You do not need an account, there is no cap on how many questions you can work through, and nothing is behind a paywall or carries 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

I do. I am Arman Kiledjian, PharmD, in California, and I write and maintain every page of this site myself. I hold the Doctor of Pharmacy degree and have passed both licensing exams, the NAPLEX and the CPJE. My pharmacist license has not yet been issued, so I currently practice as a pharmacy intern, and nothing here is written in the capacity of a licensed pharmacist. When my RPh license is issued, I will publish its number on this page.

Nobody pays me, nothing is sponsored, and no company has any input into the content. There are no affiliate links. If that ever changes, I will disclose it 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 I wrote for each topic picks the clinical variables (a patient weight, a vial strength, a set drop factor, an infusion rate) from ranges I chose 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, whether that is two decimal places, a whole number or a 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.

Every step carries its units. 240 mL × 1.25 g/mL = 300 g, not 240 × 1.25 = 300 g. Dimensional analysis is the method these pages teach, and a unitless intermediate breaks it.

What is actually verified

Five automated test suites run before I deploy anything. 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, and please 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.

I wrote the formulas, and no second person has independently reviewed them. One author checking his 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]; I put corrections up quickly, and they are the most useful thing anyone can send me.

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 judgment.

Contact

Corrections, questions, and requests for topics that are not covered yet: [email protected]. I read every one.