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Validating a calculator against hand arithmetic — what changed since

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Solved by v.malinowski in post #2

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.

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c.ramosTL2 Moderator1 Apr 2025#1

Posting this under the heading it deserves: Validating a calculator against hand arithmetic — what changed since Everything below is what sits behind that.

Working through the identity arithmetic and I would like it checked.

retatrutide has a monoisotopic mass close to 4731.3 Da. On an electrospray instrument I would expect to see the multiply charged series rather than the intact singly charged ion, so for the doubly charged species I calculate (4731.3 + 2 x 1.00728) / 2, and for the triply charged the analogous expression.

The observed values in the report sit within a few ppm of those. My question is what that actually establishes, because I have seen people treat a mass match as a purity result and I do not think it is one.

1 like 16mo

v.malinowskiTL2 Moderator Solution2 Apr 2025#2

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.

11 likes 16mo

NLoughranTL3Regular3 Apr 2025#3

v.malinowski, post #2: 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. Go to post

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.

17 likes in reply to #2 16mo

i.beaulieuTL2 Moderator4 Apr 2025 · edited#4

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.

0 likes 16mo

IMainwaringTL3Regular5 Apr 2025#5

post #4 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.

0 likes 16mo

b.adeyemiTL2 Moderator6 Apr 2025#6

Worth separating two things that post #2 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.

1 like in reply to #2 16mo

osmolal_tableTL1Member7 Apr 2025#7

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.

12 likes 16mo

so.mbekiTL2 Moderator8 Apr 2025#8

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.

25 likes 16mo

g.pemberton_ukTL3Regional · UK9 Apr 2025#9

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.

0 likes 16mo

ai.vukovicTL210 Apr 2025#10

Collapsed as off-topic by two members at trust level 3 or above

On post #6 — agreed on the reasoning, with one qualification.

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.

j.iyerTL210 Apr 2025#11

Collapsed as off-topic by two members at trust level 3 or above

Coming back to post #9, because the follow-up matters more than the original answer.

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.

physio_marchettiTL2Physiotherapist11 Apr 2025#12

0 likes 16mo

n.oseiTL2 Moderator12 Apr 2025 · edited#13

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.

0 likes 16mo

baseline_driftTL2Analytical chemist13 Apr 2025#14

post #13 answers the question as asked. The question underneath it is different.

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

20 likes 15mo

au.pereiraTL2 Moderator13 Apr 2025#15

osmolal_table, post #7: 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. Go to post

I read post #13 twice before replying, because I had assumed the opposite.

Having read the exchange above, I think I was wrong earlier in this topic and I want to say so plainly rather than quietly editing.

The correction was fair and I had been repeating something I had not checked carefully enough.

2 likes in reply to #7 15mo

two_year_lineTL3Regular14 Apr 2025#16

i.beaulieu, post #4: 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. Go to post

This follows post #13 rather than contradicting it.

0 likes in reply to #4 15mo

s.kuuselaTL2 Moderator15 Apr 2025#17

28 likes 15mo

coldchain_liuTL3Regular15 Apr 2025#18

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.

14 likes 15mo

a.ibarraTL2 Moderator16 Apr 2025#19

13 likes 15mo

l.wikstromTL2 Moderator17 Apr 2025#20

4 likes 15mo

j.habermannTL3Regular17 Apr 2025#21

b.adeyemi, post #6: Worth separating two things that post #2 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. Go to post

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.

24 likes in reply to #6 15mo

ni.stanescuTL2 Moderator18 Apr 2025#22

j.iyer, post #11: Coming back to post #9, because the follow-up matters more than the original answer. 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. Go to post

Coming back to post #20, because the follow-up matters more than the original answer.

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.

0 likes in reply to #11 15mo

BBramleyTL3Regular19 Apr 2025#23

post #22 answers the question as asked. The question underneath it is different.

3 likes 15mo

k.okaforTL2 Moderator19 Apr 2025 · edited#24

Having read the exchange above, I think I was wrong earlier in this topic and I want to say so plainly rather than quietly editing.

The correction was fair and I had been repeating something I had not checked carefully enough.

11 likes 15mo

LeitermanTL3Regular20 Apr 2025#25

IMainwaring, post #5: post #4 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. Go to post

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.

17 likes in reply to #5 15mo

g.ekstromTL2 Moderator21 Apr 2025#26

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

33 likes 15mo

r.marsdenTL3Regular21 Apr 2025#27

post #26 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.

1 like 15mo

n.serranoTL2 Moderator22 Apr 2025#28

Worth separating two things that post #24 runs together.

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.

7 likes 15mo

g.valckenaereTL3Regular23 Apr 2025 · edited#29

NLoughran, post #3: 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. Go to post

Picking up post #26: 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.

12 likes in reply to #3 15mo

f.fontaineTL2 Moderator23 Apr 2025#30

Having read the exchange above, I think I was wrong earlier in this topic and I want to say so plainly rather than quietly editing.

The correction was fair and I had been repeating something I had not checked carefully enough.

25 likes 15mo

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