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How much water?
Most calculators make you guess a water volume and see what comes out. This one starts from the mark you want to draw to and tells you the volume that gets you there.
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- Free
- Time
- Under 1 min
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The science
Why the volume is a choice, not a rule
01
Adding water does not change how much peptide is in the vial. It changes how much liquid that peptide is dissolved in, which changes the concentration, which changes how large a volume you draw for the same dose.
02
That makes the water volume a lever rather than a fixed instruction. More water gives a lower concentration and a bigger, easier-to-read draw. Less water gives a higher concentration and a smaller draw that is easier to misread.
03
Working backwards is usually the more useful direction. Decide the mark you want to land on, ideally a whole number like ten or twenty units, and the formula rearranges to give the water volume that produces it: water equals units multiplied by vial size, divided by dose multiplied by one hundred.
04
Two practical limits bound the answer. The vial has to physically hold the liquid, and most peptide vials take two to three millilitres comfortably. And the resulting draw has to stay above roughly two units, below which the spacing between graduations becomes a large share of the dose itself.
FAQ
Common questions
How much bacteriostatic water should I add to a 5 mg vial?
There is no single correct amount, because the water volume only sets the concentration. Choose the volume that makes your dose land on a readable syringe mark. For a 5 mg vial dosed at 250 mcg, 2 ml gives exactly 10 units per dose.
Can I add more water to make dosing easier?
Yes. More water lowers the concentration, which makes each dose a larger and easier-to-measure volume. The limits are the physical capacity of the vial and the capacity of your syringe.
Does adding more water weaken the peptide?
No. It does not change the total amount of peptide in the vial, only its concentration. You draw a larger volume to get the same dose.
What is bacteriostatic water?
Sterile water containing a small amount of preservative, usually benzyl alcohol, which is what allows a vial to be entered more than once. Plain sterile water has no preservative and a much shorter usable window.
Can I use sterile water instead of bacteriostatic water?
It can be used, but without a preservative the vial is intended for a single use and the usable window is far shorter. For a multi-dose vial that you will enter repeatedly over weeks, bacteriostatic water is the reason that is possible.
How do I add the water without damaging the peptide?
Common practice is to aim the stream down the inside wall of the vial rather than directly onto the powder, then swirl gently rather than shaking. Peptides are fragile molecules and vigorous agitation can degrade them.
What if the volume I need will not fit in the vial?
Use a smaller volume and accept a smaller draw, or split the dose differently. If the required volume exceeds what the vial holds, the calculator is telling you that target mark is not achievable with that vial size.
VialClock
This page calculates. Your notes app forgets.
Every tool here is stateless by design. What it cannot do is remember that your vial was mixed eleven days ago, or that a step-up is due this week.
Browse all calculatorsThis tool performs arithmetic on figures you enter, or presents a manufacturer-published schedule. It does not know your protocol, will never suggest a dose, and is not medical advice. Dosing decisions belong with a qualified prescriber.