What bacteriostatic water vial sizes are available?
Bacteriostatic water vial sizes run from small 1 mL vials up to 30 mL multi-dose vials. The size on the label is the fill volume of Bacteriostatic Water for Injection, USP: sterile water with 0.9% benzyl alcohol as a preservative. Which sizes you can actually find depends on where you buy.
- 10 mL and 30 mL are the sizes you’ll see most often for bacteriostatic water.
- 3 mL and 5 mL are common from research suppliers, which sell BAC water labeled for research use.
- 1 mL and 2 mL are offered by some research suppliers and hold enough for a single small mix.
Availability changes from seller to seller, so treat any size list as a starting point and read the label on the vial you actually receive.
How many mixes does each vial size cover?
To see how far a vial goes, divide the vial volume by the amount of water you add per reconstitution and round down. The chart below does that for the three water volumes people use most. If you still need to decide how much water to add, the BAC water to peptide ratio chart covers that step.
| Vial size | 1 mL per mix | 2 mL per mix | 3 mL per mix |
|---|---|---|---|
| 1 mL | 1 | 0 | 0 |
| 2 mL | 2 | 1 | 0 |
| 3 mL | 3 | 1 (1 mL left) | 1 |
| 5 mL | 5 | 2 (1 mL left) | 1 (2 mL left) |
| 10 mL | 10 | 5 | 3 (1 mL left) |
| 20 mL | 20 | 10 | 6 (2 mL left) |
| 30 mL | 30 | 15 | 10 |
These are on-paper numbers. A little liquid always stays behind in the vial and the needle hub, so when a plan uses every last drop (five 2 mL mixes from a 10 mL vial, for example), don’t count on the final full draw until you’ve confirmed it’s there.
Why the 28-day rule matters more than vial size
Once the stopper is punctured, a clock starts. An opened multi-dose vial is commonly dated and discarded within 28 days unless the manufacturer specifies a different date. The benzyl alcohol limits the growth of some bacteria, but it does not sterilize the vial, does not act on viruses, and does not replace aseptic technique, so the date limit still applies.
That turns the size question into a simpler one: how much water will you actually draw from this vial in 28 days? Unopened vials are a different matter; they keep until the expiration date on the label when stored as directed, usually at controlled room temperature (20–25 °C / 68–77 °F). The BAC water storage and shelf-life guide goes deeper on dating and storage.
How to match a vial size to your use
- Count the reconstitutions you expect to do in the next 28 days.
- Multiply that count by the water volume per reconstitution.
- Pick the smallest vial that covers the total, with a little margin.
Worked example: you expect two reconstitutions of 2 mL each in the 28-day window. That’s 2 × 2 = 4 mL of water. Laying the next four weeks out on our peptide calendar maker makes the count in step 1 easy.
| Vial size | Water used | Discarded at day 28 |
|---|---|---|
| 3 mL | Not enough (one 2 mL mix only) | — |
| 5 mL | 4 mL | 1 mL |
| 10 mL | 4 mL | 6 mL |
| 30 mL | 4 mL | 26 mL |
The 5 mL vial fits best here. If you instead expected five 2 mL reconstitutions (10 mL total), a 10 mL vial works on paper but leaves no margin, which is why some people keep a second small unopened vial on hand rather than jumping straight to 30 mL.
Bacteriostatic water for peptides: 10 mL vs 30 mL
For most people the real choice is between these two sizes.
- 10 mL covers ten 1 mL mixes, five 2 mL mixes, or three 3 mL mixes with 1 mL left. That’s a realistic amount to use inside 28 days for many routines.
- 30 mL usually costs less per mL on the shelf, but it holds fifteen 2 mL mixes. Unless you reconstitute often, most of it will reach the 28-day mark unused.
A lower shelf price per mL only saves money if you use the water before the discard date. The guide to choosing the best BAC water shows how to compare cost per mL you actually use.
Small vials: 1 mL, 2 mL, 3 mL and 5 mL
A 1 mL vial of BAC water covers exactly one 1 mL mix, and a 2 mL vial covers one 2 mL mix, so nothing sits open waiting to expire. The trade-off is a higher price per mL and a separate vial to open, date and track each time. A 3 mL vial covers one 3 mL mix, or one 2 mL mix with 1 mL left; a 5 mL vial covers two 2 mL mixes with 1 mL left.
Does vial size change the calculator math?
No. Concentration depends only on the peptide amount in the peptide vial and the volume of water you add to it, not on the size of the water vial you drew from. Two milliliters from a 5 mL vial and two milliliters from a 30 mL vial give the same result.
For example, a 5 mg peptide vial with 2 mL of water is 5 ÷ 2 = 2.5 mg/mL, which is 5 × 10 ÷ 2 = 25 mcg per unit on a U-100 syringe. Enter your own vial amount and water volume in the BAC water for peptides calculator to get the full breakdown.
Frequently Asked Questions
What sizes does bacteriostatic water come in?
Bacteriostatic water is sold in vials from about 1 mL up to 30 mL. 10 mL and 30 mL vials are the most common, and many suppliers also offer 3 mL and 5 mL vials. Availability varies by seller.
How many mixes can I get from a 10 mL vial of BAC water?
On paper, a 10 mL vial covers ten 1 mL reconstitutions, five 2 mL reconstitutions, or three 3 mL reconstitutions with 1 mL left over. A small amount always stays in the vial, so leave some margin when a plan uses the full volume.
Is a 30 mL vial of bacteriostatic water better value?
Only if you use it. A 30 mL vial usually costs less per mL, but an opened multi-dose vial is generally discarded 28 days after first puncture unless the manufacturer states otherwise. Whatever is left at that point is wasted, which raises the real cost per mL you use.
Does the 28-day limit apply to unopened vials?
No. The 28-day guidance applies after the vial has been punctured. Unopened vials keep until the expiration date printed on the label when stored as the label directs, usually at controlled room temperature.
Does the size of the water vial affect peptide concentration?
No. Concentration depends only on the peptide amount and the volume of water added to the peptide vial. Two milliliters drawn from a small vial or a large vial give the same concentration.