This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1.
Significant figures in the output should not exceed what the inputs support. A concentration calculated from a nominal vial mass is not known to four decimal places.
The most common input error is entering the vial mass in the concentration field. It produces a plausible number, which is why it survives.
I would want the raw data before agreeing with my own summary of it.
Post #30 is the version of this I will quote in future. One addition.
Unit-conversion tools are only as good as the assumption they make about the syringe. Ask what barrel and what graduation interval it assumed before trusting the units figure.
Noting that the question and the thing people usually mean by it are different.
That is a cleaner way of putting what I was circling around.
Answering the question post #32 raises rather than the one it answers.
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.
Stating my assumptions rather than smuggling them in.
This follows post #38 rather than contradicting it.
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.
That matches what I was told, which is not the same as knowing it.
Right — I had this wrong and I am glad to have read it before it mattered.
A saved calculation is worth more than a remembered one. Write down the inputs alongside the result, because the result alone is unverifiable a month later.
Where I part company with post #41, and it is a narrow parting.
The reconstitution calculation is total mass divided by total volume for concentration, then dose divided by concentration for volume, then volume times one hundred for units on a U-100 barrel. Three steps, and every error is in one of them.
One of those cases where knowing the mechanism does not help the decision.
I will take the caveat as seriously as the claim, which is the point of putting it there.
Answering the question post #41 raises rather than the one it answers.
Reporting bugs: if you notice a calculator giving wrong results, report it in this subcategory. Bugs are fixed when identified.
On balance I think that is right, and I would not bet much on it.
The arithmetic in post #45 is right; the assumption feeding it is the part to check.
The most common input error is entering the vial mass in the concentration field. It produces a plausible number, which is why it survives.
It took me longer than it should have to see that.
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.
Filing this under things that are true until someone shows me otherwise.
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 would rather be precise about what I do not know than vague about what I do.
Everything in post #45 holds. The case it does not cover is the one I have.
Do the arithmetic by hand the first few times, whatever tool you use afterwards. A calculator with a wrong input gives a confident wrong answer and there is nothing in the interface to tell you.
The literature is thinner on this than the confidence in the thread implies.
Rounding behaviour is where two tools disagree. One rounding to the nearest graduation and one to two decimal places will produce different advice from identical inputs.
If this contradicts something upthread, the upthread version may well be the better one.
Significant figures in the output should not exceed what the inputs support. A concentration calculated from a nominal vial mass is not known to four decimal places.
Maintaining a calculator means checking the arithmetic against hand-worked cases at each review, not checking that it still loads.
Small point, but it is the one that usually catches people.
Narrowing post #52, because the general version has more than one answer.
Dose equivalence calculator: compounds have different potencies. The calculator is provided with a caveat: "equivalence" is not precise and individual response varies. It is a rough starting point, not a dose prescription.
Not disagreeing with anyone above, just adding the bit I keep having to look up.
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.
Post #56 answers the question as asked. The question underneath it is different.
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.
This has been discussed before and I could not find the thread, so, again.
This settles it for me, at least until somebody posts a reason it should not.