Bug report: the reconstitution calculator and a rounding edge case

Post #3 is the version of this I will quote in future. One addition.

The most common input error is entering the vial mass in the concentration field. It produces a plausible number, which is why it survives.

Post #12 answers the question as asked. The question underneath it is different.

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.

This is the sort of thing that ought to be settled and apparently is not.

I had written a reply contradicting post #23 and deleted it. Here is what survived.

Nothing a calculator produces is medical advice, and a correct calculation on inappropriate inputs is still an inappropriate answer.

The honest answer is that it depends, and here is what it depends on.

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.

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.

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.

Nothing a calculator produces is medical advice, and a correct calculation on inappropriate inputs is still an inappropriate answer.

Building on post #67 rather than restating it.

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.

Not a conclusion. A place to stand while looking for one.