Revisiting: Bug report: the reconstitution calculator and a rounding edge case — setting out what I have, and where I think it stops being reliable.
Posting the calculation with the inputs, so that somebody can disagree with a step rather than with the answer.
Inputs: 5 mg in 2 mL, target 1.0 mg, U-100 barrel. Working shown below in the order I did it.
I have checked it twice by the same route, which is not the same as checking it twice.
Nothing a calculator produces is medical advice, and a correct calculation on inappropriate inputs is still an inappropriate answer.
Written in the hope of being told what I have missed.
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 variance between people here is larger than the effect being discussed.
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.
Speaking for myself and not for anyone else who has posted here.
I read post #3 twice before replying, because I had assumed the opposite.
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 #3 answers the question as asked. The question underneath it is different.
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.
Following, with nothing to contribute beyond having asked the same thing elsewhere.
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.
Someone should write this up properly, and it should probably not be me.
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.
Adding the caveat now so it does not have to be extracted later.
Taking post #8 at face value and following it one step further.
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.
The reasoning is more useful than the number, which is why I have shown it.
Post #10 and I disagree about the size of the effect, not about the direction.
Where a calculator and your own arithmetic disagree, the productive move is to find which step differs rather than to decide which is right.
That is the honest state of it as of this week.
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.
Building on post #12 rather than restating it.
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.
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.
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.
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.
Fair, and the limits you put on it are the part I will remember.
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 would put the burden of proof on the interesting explanation, not the dull one.
I read post #19 twice before replying, because I had assumed the opposite.
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.
Post #23 answers the question as asked. The question underneath it is different.
Maintaining a calculator means checking the arithmetic against hand-worked cases at each review, not checking that it still loads.
That is what the documentation says. What happens in practice is usually close.
The most common input error is entering the vial mass in the concentration field. It produces a plausible number, which is why it survives.
The confident version of this sentence would be wrong, so here is the hedged one.
Everything in post #23 holds. The case it does not cover is the one I have.
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 single observation, in a thread that deserves better than single observations.
Post #27 describes the usual case. This is about the unusual one.
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.
Adding the measurement that post #27 says would settle it.
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.