Peptide Reconstitution Calculator
Work out how much bacteriostatic water to add to your vial. Choose the draw you want on the syringe and this solves for the water volume that gets you there.
Total amount printed on the vial label.
250 mcg = 0.25 mg
Pick a round number that’s easy to read on the barrel.
Water volumes are rounded to the nearest 0.05 mL, since that is about the finest amount you can measure reliably when drawing bacteriostatic water. This is reconstitution arithmetic, not a dosing recommendation.
Already mixed your vial and just need the draw? Use the peptide dose calculator — it works the other way round, turning a water amount you have already added into syringe units.
Reconstitution has exactly one decision
The milligrams in your vial are printed on the label, and your dose comes from whatever protocol you are following. That leaves a single number genuinely up to you: how much bacteriostatic water to add. It is the only variable in reconstitution, and it is the one most calculators make you guess at by trial and error.
Water volume does not change how much peptide you have — it changes how far that peptide is spread out. Adding twice the water halves the concentration and doubles the number of units you draw for the same dose. That is the whole trade-off: a more dilute vial gives a larger draw that is easier to read accurately, while a concentrated vial gives a small draw where being off by one unit costs you proportionally more.
Working backwards from the draw
Because a bigger draw is easier to read, the sensible way to reconstitute is to decide what you want to see on the barrel first and then solve for the water. Pick a round figure — 20 units, 25, 50 — and this calculator returns the volume that lands your dose exactly there.
The arithmetic inverts the standard reconstitution identity. Where units are dose (mcg) × water (mL) ÷ (10 × vial mg), solving for water gives water (mL) = units × 10 × vial (mg) ÷ dose (mcg). One caveat the formula alone will not tell you: the answer often lands on a volume like 1.37 mL, which nobody can measure. The result is rounded to the nearest 0.05 mL and the calculator shows the draw you actually get at that measurable volume, rather than quietly reporting a number you cannot follow.
Reconstitution calculator — FAQ
How much bacteriostatic water should I add to a peptide vial?+
There is no single correct amount — the water volume sets the concentration, not the total peptide. The practical answer is to add whatever volume makes your dose land on a round, easy-to-read number of units. Enter your vial size, dose, and target draw above and this calculator solves for that volume directly.
Does adding more bacteriostatic water make the dose weaker?+
It makes the solution more dilute, but your dose is unchanged — you simply draw a larger volume to get the same amount of peptide. More water means a bigger, easier-to-read draw; less water means a smaller, more concentrated one. The peptide in the vial never changes.
Why does the calculator round the water volume?+
Because you add water with a syringe, and roughly 0.05 mL is the finest volume most people can measure reliably. An instruction like "add 1.37 mL" is not something you can actually follow, so the result is rounded to the nearest measurable step and the calculator shows the draw you really get at that volume.
What happens if I add the wrong amount of water?+
Nothing is ruined — the peptide in the vial is unchanged. Your concentration is simply different from what you planned, so the number of units for your dose changes. Measure how much water actually went in, then recalculate the draw from that figure.