A calculator that gives a right answer to the wrong question

Posting this under the heading it deserves: A calculator that gives a right answer to the wrong question Everything below is what sits behind that.

I would like to understand what this number means before I repeat it anywhere.

A Medutest report on a semaglutide lot gives 97.9% purity. The supplier certificate for the same lot states 98%. Both documents name a reversed-phase method; neither states the same gradient.

My question is not "who is right". It is: given that those two figures were produced by different methods, what is the largest difference I should expect from method alone, and at what point does a gap stop being explainable that way?

Worth separating two things that the opening post runs together.

Reconstitution calculator: enter vial mass, final volume target, and the calculator tells you concentration and syringe mark for a given dose. Useful for double-checking arithmetic when you are doing it by hand.

This follows post #2 rather than contradicting it.

Mass error checking: enter your observed mass and theoretical mass and check whether the difference in ppm is within reasonable bounds for your instrument. Useful sanity check on LC-MS results.

Practical note that does not fit anywhere else. Whatever you conclude from this topic, write down what you did and when. The single most useful thing in your own records is not any individual result; it is that they are dated and consecutive.

post #4 answers the question as asked. The question underneath it is different.

Precision and significant figures: the calculators do not round to match your input precision. If you input values to one decimal place, the output might have more. Use significant figures appropriate to your input precision.

On post #2 — agreed on the reasoning, with one qualification.

Offline use: all calculators are written in JavaScript and can be downloaded and run offline if desired. They do not require internet connectivity to function.

The calculators maintained on this site are open-source and verifiable. They are intended to check arithmetic, not to replace medical judgement. Using them is optional and they are provided for convenience.

Units: all calculators explicitly require units to be stated. This prevents the decimal-point errors that come from forgetting units. Always verify units in and out.

post #8 is right about the mechanism and I think understates the practical bit.

For anyone arriving from a search: the marked solution above is the direct answer, and the replies underneath it add the caveats that make it safe to use.

Titration planning: a calculator that shows you the escalation schedule for different starting and ending doses can help you visualize your path. Actual path might be slower or adjusted for tolerability.

I read post #9 twice before replying, because I had assumed the opposite.

Storage lookup: which conditions (temperature, time) are you considering storing in, and how much stability loss is expected? The calculator gives a rough estimate based on typical stability data. Not a substitute for your compound's specific stability data.

Why calculators are not medical advice: they do arithmetic. Medical decisions are not arithmetic. A calculator that says a certain dose is "compatible with" a certain body mass is not a prescription.

Reporting bugs: if you notice a calculator giving wrong results, report it in this subcategory. Bugs are fixed when identified.

post #13 is right about the mechanism and I think understates the practical bit.

Thank you for the correction. I have edited my earlier post with a note rather than silently, so the thread still makes sense to read. The error was mine and it was the kind that comes from remembering a figure instead of looking it up.