Peptide Reconstitution Calculator
Pick your vial. Pick how much water you mixed it with. Pick the dose you want. We will tell you exactly how many units to draw on a standard insulin syringe, and show the math so you can double-check it.
The math, in plain English
Peptide reconstitution math has three steps. None of it is mysterious. Here is the same logic the calculator above is using, written out:
- 1
Find the concentration.
Take the milligrams of peptide that came in the vial, and divide by the milliliters of bacteriostatic water you added. That gives you mg per mL. Example: a 10 mg vial with 2 mL of water gives 5 mg/mL, which is also 5,000 mcg/mL.
- 2
Find the volume per dose.
Divide your desired dose by the concentration. Same units on top and bottom. Example: 250 mcg ÷ 5,000 mcg/mL = 0.05 mL per dose.
- 3
Convert to insulin syringe units.
A standard U-100 insulin syringe is calibrated so 100 units fits in 1 mL. So multiply your volume in mL by 100. Example: 0.05 mL × 100 = 5 units. Easy.
About bacteriostatic water
Bacteriostatic water (sometimes called “BAC water”) is sterile water with a small amount of benzyl alcohol added as a preservative. The benzyl alcohol slows bacterial growth, which is what lets you draw from the same vial more than once over several weeks without it becoming a science experiment.
28-day rule of thumb
Per USP General Chapter 797 and the USP beyond-use-date guidance, a peptide reconstituted with bacteriostatic water and stored refrigerated (2 to 8 degrees Celsius) typically has a 28-day beyond-use date. Real fridges are not perfect lab fridges, so be conservative if storage gets sketchy.
Important: this is a math tool, not medical advice
- The calculator does not decide whether you should take a peptide, what dose is right for you, or whether your specific vial is actually what the label says.
- Dose decisions are between you and a prescribing clinician. We show vial sizes that are common in the market, not recommendations.
- Many research peptides are not FDA-approved for human use. Quality, purity, and even the actual mg of peptide in a vial can vary by vendor.
- If a result looks weird (very large or very small), recheck which unit you picked (mg vs mcg). Mixing them up is the most common mistake.
Common questions
What if my dose volume comes out to less than 1 unit?
That means your peptide is too concentrated for that dose. Use less water (or split the vial) so each dose lands at a measurable volume, ideally a few units or more.
What if my dose volume is more than 1 mL?
Then the dose will not fit in a single 1 mL insulin syringe. Either use more bacteriostatic water (lower concentration, smaller volume per dose), or split the dose into two injections.
Does it matter what kind of syringe I use?
The unit math here assumes a U-100 insulin syringe, which is the standard. If you have a U-40 syringe (rare in the US, more common in some veterinary contexts), the unit math is different. Stick with U-100 unless you know exactly what you have.
How do I know my vial actually contains what the label says?
For FDA-approved compounded medications dispensed by a licensed pharmacy, the label is regulated. For research peptides bought online, you essentially have to trust the vendor or arrange your own third-party testing. This is one reason vendor selection matters more than people realize.