How much water to add
Work backwards. Choose the concentration you want, or the unit count you want a given amount to land on, and get the millilitres to add.
Volume table
| Vial | 1 mL | 2 mL | 3 mL | 5 mL |
|---|---|---|---|---|
| 2 mg | 2 mg/mL · 20 mcg/unit | 1 mg/mL · 10 mcg/unit | 0.67 mg/mL · 6.7 mcg/unit | 0.4 mg/mL · 4 mcg/unit |
| 5 mg | 5 mg/mL · 50 mcg/unit | 2.5 mg/mL · 25 mcg/unit | 1.67 mg/mL · 16.7 mcg/unit | 1 mg/mL · 10 mcg/unit |
| 10 mg | 10 mg/mL · 100 mcg/unit | 5 mg/mL · 50 mcg/unit | 3.33 mg/mL · 33.3 mcg/unit | 2 mg/mL · 20 mcg/unit |
| 15 mg | 15 mg/mL · 150 mcg/unit | 7.5 mg/mL · 75 mcg/unit | 5 mg/mL · 50 mcg/unit | 3 mg/mL · 30 mcg/unit |
| 20 mg | 20 mg/mL · 200 mcg/unit | 10 mg/mL · 100 mcg/unit | 6.67 mg/mL · 66.7 mcg/unit | 4 mg/mL · 40 mcg/unit |
| 30 mg | 30 mg/mL · 300 mcg/unit | 15 mg/mL · 150 mcg/unit | 10 mg/mL · 100 mcg/unit | 6 mg/mL · 60 mcg/unit |
| 50 mg | 50 mg/mL · 500 mcg/unit | 25 mg/mL · 250 mcg/unit | 16.67 mg/mL · 166.7 mcg/unit | 10 mg/mL · 100 mcg/unit |
| 60 mg | 60 mg/mL · 600 mcg/unit | 30 mg/mL · 300 mcg/unit | 20 mg/mL · 200 mcg/unit | 12 mg/mL · 120 mcg/unit |
The volume is a choice
Nothing about the vial dictates the volume. The mass on the label is fixed; the solvent sets how that mass is spread out. Less solvent means a higher concentration and fewer units per draw, which is easier to fit in a small barrel but harder to read precisely. More solvent means more units per draw, easier to read, but a 1 mL barrel runs out sooner. The water guide explains how to pick a volume that gives round numbers, and the vial tables show every pairing.
Questions
How much bacteriostatic water should I add to a 5 mg vial?
Any volume the vial holds; the choice sets the concentration, not the mass. 1 mL gives 5 mg/mL, 2 mL gives 2.5 mg/mL, 3 mL gives 1.67 mg/mL. Pick the volume that puts your amount per draw on a round, readable unit count.
Can I add more water later?
Arithmetically yes: recompute the concentration with the total volume. 5 mg in 2 mL plus 1 mL more is 5 mg in 3 mL. Whether a vial should be topped up is not a math question and this site does not address it.
What is bacteriostatic water?
Sterile water containing 0.9% benzyl alcohol, sold in multi-use vials. It is the solvent most lyophilized peptide labels name. The math is identical for any solvent.
What if the volume I need does not fit the vial?
Most lyophilized vials are 2 mL or 3 mL glass. If the calculator asks for more than the vial holds, accept a higher concentration (fewer units per draw) or use a larger barrel.
Brands we recommend. We are independent and have no affiliation with any brand: no affiliate links, no referral codes, no paid placements. These are the suppliers whose testing and certificates hold up when we check them.
- Licensed Peptides two accredited labs on every lot, certificates public, card and Apple Pay checkout
- Core Peptides long track record, public certificates, wide catalog
- Ascension Peptides public third-party testing, clear pricing