Enter the vial size, how much bacteriostatic water you added, and your target dose. Get the concentration, the volume to draw, and — the number most people actually need — the units to fill on a U-100 insulin syringe.
Reconstitution is just dilution. When you add bacteriostatic water to a lyophilized (freeze-dried) peptide vial, the peptide dissolves into that volume of liquid. The concentration is the peptide amount divided by the water you added:
concentration (mg/mL) = vial amount (mg) ÷ bac water (mL)
To pull a specific dose, you divide the dose by that concentration to get the
volume to draw. Because a U-100 insulin syringe is marked so that
100 units = 1 mL, multiplying the draw volume by 100 gives the unit mark
to fill to — the number most people read off the barrel:
volume (mL) = dose (mg) ÷ concentration (mg/mL)
units (U-100) = volume (mL) × 100
A 10 mg vial reconstituted with 2 mL of
bac water gives 10 ÷ 2 = 5 mg/mL. For a 0.5 mg
(500 mcg) dose: 0.5 ÷ 5 = 0.1 mL, which is
0.1 × 100 = 10 units on a U-100 syringe.
The water you add doesn't change the total amount of peptide in the vial — only how concentrated each draw is. More water means a larger, easier-to-measure draw at a lower concentration; less water means a smaller draw. Pick a volume that lands your typical dose on a readable mark. This tool only does the arithmetic; it does not recommend a dose or a dilution.