Bacteriostatic water calculator
The question you ask while the vial is still sealed. Put in the vial size and your dose — see how much water each option needs, the draw it gives you, and which ones land on a mark you can read.
15 mixes per bottle
This barely fills a 0.5 ml barrel. A 0.3 ml is marked every ½ unit instead of every 1 — same dose, easier to hit exactly.
✓ Lands on a printed mark
✓ Lands on a printed mark
More than a 3 ml vial holds
Our pick
2 ml
draws 10 units for a 500 mcg dose
This one puts the draw on a mark printed on the barrel, so you can see it rather than estimate it.
Why there isn’t one answer
Water doesn’t change how much peptide is in the vial — only how spread out it is. Less water means a smaller draw, which gets hard to measure. More water means a bigger draw, which eventually runs off the end of the barrel. Everything between those is a preference, so the table shows the trade instead of picking for you.
Share this calculation
Common questions
- How much bacteriostatic water should I add to a 5 mg vial?
- There's no single right amount — water doesn't change how much peptide is in the vial, only how spread out it is. What it changes is your draw. This calculator shows 1, 2, 3 and 5 ml side by side with the draw each produces, and marks the ones that land on a printed gradation.
- Does more water mean a weaker dose?
- No. The same dose is the same amount of peptide either way — you just draw a larger volume of a more dilute solution to get it. More water makes the draw bigger and easier to measure accurately, until it runs off the end of the barrel.
- Why does landing on a mark matter?
- A 0.5 ml barrel is printed every 1 unit. If your dose works out to 12.5 units you're estimating halfway between two lines every single time. Choosing water that puts the draw on a printed line removes that.
- Can I put 5 ml into a 3 ml vial?
- No — the glass has a size. The calculator dims amounts your vial can't hold, and you can tell it if your vial is bigger.