Free peptide reconstitution calculator
Peptide Calculator
Enter how much peptide is in the vial, how much bacteriostatic water you added, and the dose. You get the exact units to draw on a U-100 insulin syringe, and the math behind it.
Reconstitution calculator
Example values are loaded. Replace them with the numbers on your own vial.
How the peptide calculator works
A lyophilized (freeze-dried) peptide is sold as a powder, measured in milligrams. Once you add liquid, the powder dissolves evenly, and every drop of the solution carries the same amount of peptide. The calculator uses three steps, all simple division and multiplication:
Volume to draw (mL) = dose (mg) ÷ concentration (mg/mL)
Syringe units = volume (mL) × 100
The last step works because a U-100 insulin syringe holds 100 units in 1 mL, so one unit is always 0.01 mL, whatever the size of the syringe barrel.
Worked example
A 10 mg vial mixed with 2 mL of bacteriostatic water gives 10 ÷ 2 = 5 mg/mL. For a 2 mg dose you need 2 ÷ 5 = 0.4 mL, and 0.4 × 100 = 40 units. The vial holds 10 ÷ 2 = 5 doses of that size.
Change one number and everything moves together. With 1 mL of water instead of 2 mL, the same vial is twice as concentrated (10 mg/mL), so the same 2 mg dose becomes 20 units. Less water means smaller draws; more water means larger, easier-to-read draws.
Choosing how much water to add
The amount of water does not change how much peptide you get. It only changes the volume that carries it. Two practical rules help:
- Aim for draws that land on marked lines. Very small draws (under about 2 units) are hard to measure accurately. If your dose comes out at 1.5 units, adding more water spreads it over more units.
- Keep the draw inside your syringe. If a dose comes out above 30, 50 or 100 units, it will not fit a 0.3, 0.5 or 1 mL syringe in one draw. Less water makes the draw smaller.
If you already know the number of units you want each dose to be, the BAC water calculator works backwards and tells you exactly how much water to add.
Check the unit before you calculate
Most dosing mistakes come from units, not arithmetic. 250 mcg is 0.25 mg, a thousand times smaller than 250 mg. The calculator refuses a dose larger than the whole vial, which catches most mg/mcg mix-ups. The mcg to mg converter and the guide to mg, mcg, IU and units cover this in more detail. Products labelled in international units (IU), such as HCG and somatropin, use the IU calculator instead.
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Frequently asked questions
How many units is 1 mL on an insulin syringe?
On a U-100 insulin syringe, 1 mL is 100 units, so each unit is 0.01 mL. A 0.3 mL syringe holds 30 units and a 0.5 mL syringe holds 50 units.
Does adding more water weaken the peptide?
No. The total amount of peptide in the vial stays the same. More water lowers the concentration, so each dose takes up more units on the syringe, but the dose in mg is unchanged.
Why does the calculator say my dose is larger than the vial?
Usually because the dose is in mcg but the mg button is selected, or the reverse. 250 mcg is 0.25 mg. Switch the dose unit and the result will make sense.
Can I use this calculator with a U-40 syringe?
No. The units here assume a U-100 syringe, where 100 units equal 1 mL. On a U-40 syringe, 40 units equal 1 mL, so the same unit marking holds 2.5 times more liquid. Use the mL result instead, or use a U-100 syringe.
Does this calculator tell me what dose to take?
No. It only converts the numbers you enter. Your dose has to come from a licensed clinician or your prescription label.