Free tool · no download needed
Enter your vial and the bacteriostatic water you are adding, and this works out the concentration and exactly where to draw to on a U-100 insulin syringe. Same maths the app runs — use it here without installing anything.
This calculator does the arithmetic on the numbers you enter. It does not recommend a dose. Reconstitution and dosing decisions belong with you and your prescriber.
Three steps, and the calculator shows all three so you can check it against your own arithmetic.
The peptide in the vial divided by the water you add. A 10 mg vial with 2 mL of bacteriostatic water is 5 mg/mL. Adding more water does not change how much peptide is in the vial — it only changes how much liquid each dose comes in.
Your dose divided by the concentration. A 250 mcg dose at 5 mg/mL is 0.25 mg ÷ 5 mg/mL = 0.05 mL.
On a U-100 insulin syringe, 100 units is 1 mL, so every unit mark is 0.01 mL. That 0.05 mL draw is the 5-unit mark. The units are volume, not compound — the same 5-unit draw is a completely different dose if you reconstituted the vial differently.
A starting point for the numbers people ask about most. Enter your own above rather than assuming one of these matches your vial.
| Vial | Water | Concentration | 250 mcg dose | 500 mcg dose |
|---|---|---|---|---|
| 5 mg | 1 mL | 5 mg/mL | 5 units | 10 units |
| 5 mg | 2 mL | 2.5 mg/mL | 10 units | 20 units |
| 10 mg | 1 mL | 10 mg/mL | 2.5 units | 5 units |
| 10 mg | 2 mL | 5 mg/mL | 5 units | 10 units |
| 10 mg | 3 mL | 3.33 mg/mL | 7.5 units | 15 units |
| 15 mg | 3 mL | 5 mg/mL | 5 units | 10 units |
| 20 mg | 2 mL | 10 mg/mL | 2.5 units | 5 units |
Less water is not a stronger dose. The vial holds what it holds. Reconstituting with less water means each dose is a smaller, harder-to-measure draw — it does not give you more compound.
Divide the peptide in the vial by the bacteriostatic water you add to get the concentration. Divide your dose by that concentration to get the volume to draw. On a U-100 insulin syringe each 0.01 mL is one unit mark, so a 0.20 mL draw is the 20-unit line. The calculator above does all three steps and shows you the mark.
There is no single right answer — the water volume sets the concentration, not the total dose. More water makes each dose a larger, easier-to-measure draw; less water makes the vial last longer in the fridge. 2 mL into a 10 mg vial gives 5 mg/mL, which puts a 250 mcg dose at the 5-unit mark. Enter your own numbers above to see where your dose lands.
On a U-100 syringe, 100 units is 1 mL. Each unit mark is 0.01 mL. The units are a volume measurement, not a dose of peptide — the same 10-unit draw is a different amount of compound depending on how you reconstituted the vial.
IU measures biological activity, not mass, and the conversion factor is different for every compound — there is no universal number. A vial labelled in IU can only be dosed in IU. The calculator locks both menus to one family for exactly this reason, and the app does the same.
Bacteriostatic water contains 0.9% benzyl alcohol as a preservative and is typically discarded 28 days after first puncture. Reconstituted peptide stability varies by compound. Follow the guidance that came with your vial and your prescriber's direction — this calculator does arithmetic, it does not advise on storage.
Yes, entirely, with nothing to install and no account. The same calculator is built into the BioHack Track app for iPhone and Android, which also tracks the vial's remaining doses as you log.
The app runs this same calculation, then remembers it — every dose you log comes off the vial, so you always know how many are left and when to reorder. Free, unlimited.