BAC Water Calculator

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Your peptide vials

Peptide nameWater (mL)

BAC water bottle size

30 mL is the most common bottle size.

Your results

4 mL

total bacteriostatic water needed

Number of vials2

Bottle size30 mL

Bottles to order1

VOLUME IS NOT THE ONLY LIMIT

An opened bottle of bacteriostatic water is generally considered good for about 28 days after the first puncture, because the benzyl alcohol preservative only holds for so long. Ordering by total volume alone can therefore mislead you on a long protocol: if the volume above spans several months you will still be opening a fresh bottle roughly every 28 days, and part of each opened bottle may go unused. Plan around how quickly you actually draw from a bottle, not just the litres of arithmetic.

DISCLAIMER

This calculator is for educational reference only. Always consult a healthcare provider before using any peptide.

§ HOW THIS WORKS

What is bacteriostatic water?

Bacteriostatic water (BAC water) is sterile water that contains 0.9% benzyl alcohol as a preservative. The benzyl alcohol prevents bacteria from growing in the water, making it safe to use multiple times from the same vial over 28-30 days.

It is the standard diluent for reconstituting lyophilized (freeze-dried) peptides. Do not confuse it with sterile water for injection, which contains no preservative and must be used immediately after opening.

BAC water vs sterile water

Feature	BAC Water	Sterile Water
Preservative	0.9% benzyl alcohol	None
Multi-dose use	Yes (28-30 days)	No (single use)
Best for	Peptides dosed multiple times	Single-use reconstitution
Storage after opening	Room temp, up to 28 days	Discard unused portion
Cost	$3-8 per 30 mL vial	$2-5 per vial

How much BAC water per vial?

There is no single right answer. Common amounts are 1-3 mL per peptide vial. The amount only changes the concentration, not the total peptide. The trade-offs:

Less water (1 mL): Stronger concentration, smaller injection volume. Harder to measure precisely.
Standard (2 mL): Good balance of concentration and measurability. Most common choice.
More water (3 mL): Weaker concentration, larger injection volume. Easier to measure small doses.

FAQ

How many vials can I reconstitute with one 30 mL bottle?

At 2 mL per vial (the most common amount), a single 30 mL bottle reconstitutes 15 peptide vials. Most people running 1-2 peptides need only one bottle per month.

Can I reuse BAC water after opening?

Yes. The benzyl alcohol preservative allows multi-dose use for up to 28 days after first puncture. Always use a new sterile needle each time you draw.

Where do I buy bacteriostatic water?

BAC water is available over the counter from most pharmacies, medical supply stores, and online retailers. Typical cost is $3-8 per 30 mL vial.

Bacteriostatic Water Calculator