Topic summary

Second pass at: The mass-error checker and its intended scope

Data & Tools › Calculators site feedback worked example concentration maths Solved Pinned

This is a generated summary. It shows the 9 most-liked posts from a topic of 75, in their original order, with the accepted answer included where one exists. It is a reading aid and it will miss nuance — the full topic is the record.

n.vukovicTL2 Moderator19 Aug 2025#3

h.ramos, post #1: Posting this under the heading it deserves: Second pass at: The mass-error checker and its intended scope Everything below is what sits behind that. Working through the identity arithmetic and I would like it checked. tirzepatide has a monoisotopic mass close to 4813.5 Da. On an electrospray instrument I would expect to see the multiply… 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.

25 likes in reply to #1 11mo

r.petrovTL2 Moderator Solution28 Aug 2025#7

n.vukovic, post #3: 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

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.

7 likes in reply to #3 11mo

ar.petrovTL2 Moderator4 Sep 2025#11

I read post #9 twice before replying, because I had assumed the opposite.

Two things before anyone answers the substance.

First, the context in the first post is clear and specific. Second, the question is framed so that an answer can actually address it. Both are the norm here and both matter more than they sound.

25 likes 11mo

bench_entryTL3Regular25 Sep 2025#24

ppm_error, post #6: 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

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.

25 likes in reply to #6 10mo

integrator_logTL3Regular30 Sep 2025#28

d.bramley, post #10: Worth separating two things that post #6 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

On post #24 — agreed on the reasoning, with one qualification.

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.

33 likes in reply to #10 10mo

batchlogTL3Regular27 Oct 2025#48

KStephanopoulos, post #31: 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

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.

28 likes in reply to #31 9mo

g.valckenaereTL3Regular5 Nov 2025#56

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.

26 likes 9mo

l.piresTL2 Moderator22 Nov 2025 · edited#70

n.krastev, post #43: 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. Go to post

Two things before anyone answers the substance.

First, the context in the first post is clear and specific. Second, the question is framed so that an answer can actually address it. Both are the norm here and both matter more than they sound.

33 likes in reply to #43 8mo

compounding_ruthTL4Pharmacist25 Nov 2025#73

Leiterman, post #60: Picking up post #57: that is the part I would want checked first. 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

29 likes in reply to #60 8mo

Read the full topic (75 posts)

Suggested topics

Topic	Participants	Replies	Views	Activity
Coming back to: Feature request: should a dose-equivalence tool exist at all? Data & Tools › Calculators syringe units concentration maths worked example site feedback Solved Feature request: should a dose-equivalence tool exist at all? I have a specific reason for asking rather than idle curiosity, and the context is below. Posting the method first, because I know what the first…	+37	41	725	7mo
Feature request: should a dose-equivalence tool exist at all? Data & Tools › Calculators site feedback worked example concentration maths syringe units Closed Feature request: should a dose-equivalence tool exist at all? — that is the question, and I have not found it answered plainly anywhere I have looked. Posting the method first, because I know what the first…	+21	25	4.8k	18mo
A calculator that gives a right answer to the wrong question Data & Tools › Calculators concentration maths worked example site feedback syringe units Posting this under the heading it deserves: A calculator that gives a right answer to the wrong question Everything below is what sits behind that. I would like to understand what this number means before I…	+32	36	1.9k	17h
Follow-up: Why the titration planner refuses to produce a schedule below a floor Data & Tools › Calculators worked example syringe units site feedback The question in the title: Why the titration planner refuses to produce a schedule below a floor I will give what I have already checked below so nobody repeats it. I would like to understand what this number…	+120	146	14k	10mo
Bug report: the reconstitution calculator and a rounding edge case Data & Tools › Calculators worked example site feedback syringe units concentration maths Bug report: the reconstitution calculator and a rounding edge case — setting out what I have, and where I think it stops being reliable. Working through the identity arithmetic and I would like it checked.…	+68	72	28k	4mo

Related topics — sharing the tags site feedback, worked example, concentration maths

Topic	Participants	Replies	Views	Activity
A 10 mg vial reconstituted three different ways, compared Practice › Reconstitution bacteriostatic water worked example concentration maths Posting this under the heading it deserves: A 10 mg vial reconstituted three different ways, compared Everything below is what sits behind that. Practical question with the units stated, because I have seen…	+30	34	55k	17h
Choosing a concentration on purpose rather than by accident Practice › Reconstitution concentration maths worked example syringe units Solved On the subject in the title: Choosing a concentration on purpose rather than by accident Working notes rather than a conclusion. Reporting something rather than asking about it, in case the pattern is useful…		2	719	1mo
Reconstituting a multi-strength kit without mixing yourself up — what changed since Practice › Reconstitution concentration maths syringe units bacteriostatic water On the subject in the title: Reconstituting a multi-strength kit without mixing yourself up — what changed since Working notes rather than a conclusion. Practical question with the units stated, because I…	+42	46	1k	7h
Follow-up: Bug report: the reconstitution calculator and a rounding edge case Data & Tools › Calculators concentration maths site feedback syringe units On the subject in the title: Bug report: the reconstitution calculator and a rounding edge case Working notes rather than a conclusion. Working through the identity arithmetic and I would like it checked.…	+58	63	24k	5mo
Why we ask for units every single time, with three examples of what goes wrong Start Here › How to Ask worked example onboarding beginner friendly guidelines Why we ask for units every single time, with three examples of what goes wrong — that is the question, and I have not found it answered plainly anywhere I have looked. Question in the title. Context below,…	+118	135	2.2k	11d