How the reconstitution math works
Most research peptides ship as a freeze-dried (lyophilized) powder. Before use, the powder is dissolved in bacteriostatic (BAC) water, and every dose after that is a matter of drawing the right volume of that solution. The calculator does three steps:
- Concentration: vial amount ÷ BAC water volume. A 10 mg vial mixed with 2 mL of BAC water is 5 mg/mL, or 5,000 mcg per mL.
- Volume per dose: your dose ÷ concentration. A 250 mcg dose from that vial is 250 ÷ 5,000 = 0.05 mL.
- Syringe units: a U-100 insulin syringe holds 100 units per 1 mL, so 0.05 mL = 5 units on the syringe.
Choosing how much BAC water to add
The amount of water doesn’t change how much peptide is in the vial — it only changes how concentrated each drop is. More water means a larger, easier-to-measure draw per dose; less water means a smaller injection volume. Many people pick a water volume that makes their usual dose land on a round, easy-to-read number of units (for example 10 or 20 units) rather than something like 3.5 units, which is hard to measure accurately on a 100-unit syringe.
If your dose comes out under about 5 units, consider adding more water so the measurement error of the syringe markings is a smaller share of the dose. If it comes out over 100 units (more than 1 mL), you’d need more than one full syringe — use less water or a larger syringe.
Using the presets
Picking a peptide from the preset list fills in a commonly reported vial size, BAC water volume, and dose so you can see the math immediately. Those presets are starting points drawn from common practice, not recommendations — always replace them with the numbers on your actual vial label and the dose you and your clinician have decided on. You can also open the calculator pre-filled from any page in the Peptide Database.
Frequently asked questions
How many units is 250 mcg from a 5 mg vial with 2 mL of water?
A 5 mg vial in 2 mL is 2,500 mcg per mL. 250 mcg ÷ 2,500 = 0.1 mL, which is 10 units on a U-100 insulin syringe.
Does adding more BAC water weaken the peptide?
No. The total amount of peptide in the vial is the same; more water just spreads it across more volume, so you draw more units for the same dose.
What does U-100 mean on an insulin syringe?
U-100 means the syringe is calibrated for 100 units per milliliter. A 1 mL syringe has 100 unit marks, a 0.5 mL syringe has 50, and a 0.3 mL syringe has 30 — the volume per unit (0.01 mL) is the same on all of them.
Can I use this calculator with a mg dose instead of mcg?
Yes. Switch the dose unit to mg and the calculator converts it (1 mg = 1,000 mcg) before doing the math.