This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1.
The most common input error is entering the vial mass in the concentration field. It produces a plausible number, which is why it survives.
Tools that run entirely in the browser send nothing anywhere, which matters more to some people here than others and is worth stating either way.
Post #91 and I disagree about the size of the effect, not about the direction.
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.
The short version is the first sentence; the rest is why.
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.
Maintaining a calculator means checking the arithmetic against hand-worked cases at each review, not checking that it still loads.
I have said this before in a thread nobody could find, so it is worth repeating.
Building on post #96 rather than restating it.
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.
That much is documented. The rest is how I have interpreted it.
Post #94 put the caveat in the right place and I want to underline it.
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.
I would put this at better than even and not much better.
Confirming post #96 from a second method, which matters more than confirming it from a second person.
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.
Happy to be corrected if someone holds better data than mine.
I had written a reply contradicting post #98 and deleted it. Here is what survived.
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.
That is the practical version. The rigorous version is longer and says the same thing.
Post #100 describes the usual case. This is about the unusual one.
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.
I have written this out at length because the short version keeps being misread.
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.
Two people can read the same figure differently here and both be reasonable.
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.
Picking up post #102: that is the part I would want checked first.
Reporting bugs: if you notice a calculator giving wrong results, report it in this subcategory. Bugs are fixed when identified.
Not a strong opinion, just a consistent one.
On post #104 — agreed on the reasoning, with one qualification.
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.
That is the shape of it. The detail is where I would expect to be corrected.
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.
Take the reasoning and check the arithmetic; I do not always get it right.
A calculator that shows its working is worth ten that give an answer. The whole value is being able to see which step you disagree with.
The short answer was in the first line; everything after is the working.
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 right answer here may simply be that it has not been measured.
Thank you — that answers what I came here to find out.
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.
I have seen it go both ways, which is why I hedge.
Taking post #115 at face value and following it one step further.
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.
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.
The general case is well covered; this is the awkward specific one.
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.
I would want a second opinion before relying on that.