Peptide reconstitution calculator
Enter the vial strength, the bacteriostatic water you plan to add, and the amount per draw. The calculator returns the exact syringe volume in millilitres and U-100 insulin-syringe units, and checks that your water volume fits the vial.
How the calculation works
Reconstitution is one division carried through three units. Adding bacteriostatic water to a vial fixes a concentration; every draw is then just your target amount divided by that concentration.
- Concentration
vial mg × 1000 ÷ water mL = mcg/mLA 5 mg vial in 2 mL of water holds 2,500 mcg in every millilitre. - Draw volume
target mcg ÷ concentration = mLA 250 mcg amount at 2,500 mcg/mL needs 0.1 mL. - Syringe units
draw mL × 100 = U-100 units0.1 mL reads as 10 units on an insulin syringe.
| Vial | Water | Concentration | 250 mcg |
|---|---|---|---|
| 5 mg | 1 mL | 5,000 mcg/mL | 5 units |
| 5 mg | 2 mL | 2,500 mcg/mL | 10 units |
| 10 mg | 2 mL | 5,000 mcg/mL | 5 units |
| 10 mg | 3 mL | 3,333 mcg/mL | 7.5 units |
| 15 mg | 3 mL | 5,000 mcg/mL | 5 units |
| 20 mg | 2 mL | 10,000 mcg/mL | 2.5 units |
How to reconstitute a peptide
Once the calculator has planned your concentration, the physical steps are short. Handle the vial gently — peptides are sensitive to heat and agitation.
Reconstitution vocabulary
- Reconstitution
- Dissolving a freeze-dried (lyophilized) peptide powder back into liquid form by adding a measured volume of diluent, so it can be drawn accurately.
- Lyophilized
- Freeze-dried under vacuum. Removing water this way keeps the peptide stable in storage; adding water back is reconstitution.
- Concentration
- How much peptide sits in each millilitre of solution, in mcg/mL. It is fixed the moment you choose a water volume for a given vial.
- Bacteriostatic water
- Sterile water with 0.9% benzyl alcohol that inhibits bacterial growth, the standard multi-use diluent for research peptides.
Peptide calculator questions
How do you calculate peptide reconstitution?
Divide the vial's peptide mass by the volume of bacteriostatic water added to get the concentration (for example, 5 mg in 2 mL is 2,500 mcg/mL). Divide your target amount by that concentration to get the draw volume in millilitres, then multiply by 100 to read it in U-100 insulin-syringe units.
What is bacteriostatic water and why is it used?
Bacteriostatic water is sterile water containing 0.9% benzyl alcohol, which suppresses bacterial growth so a reconstituted vial stays usable across multiple draws. It is the standard diluent for reconstituting lyophilized research peptides. Sterile or plain water lacks the preservative and is better suited to single-use preparation.
How much bacteriostatic water should I add to a peptide vial?
There is no single correct volume — it sets the concentration. More water makes a dilute solution that is easier to measure in small units; less water makes a concentrated solution that draws a tiny volume. Most researchers add 1–3 mL and keep the total under the vial's fill capacity. Use the calculator to see how each volume changes the syringe reading.
What does U-100 mean on an insulin syringe?
U-100 means the syringe is graduated for insulin at 100 units per millilitre, so 100 units equals 1 mL and 10 units equals 0.1 mL. The calculator converts your millilitre draw into these units because U-100 syringes are the most precise way to measure the small volumes peptide work involves.
What is the difference between milligrams and micrograms in dosing math?
One milligram (mg) equals 1,000 micrograms (mcg). Vial strengths are labelled in milligrams while target amounts are usually expressed in micrograms, so the calculator multiplies vial milligrams by 1,000 before dividing by the water volume to keep the units consistent.
Why does the calculator warn that the draw exceeds the syringe?
A U-100 insulin syringe holds 1 mL (100 units). If your chosen concentration is too dilute for the target amount, the required draw is larger than the barrel and cannot be measured in one pull. Add less water for a stronger concentration, or use a larger syringe.
Does more bacteriostatic water change the total amount of peptide?
No. The vial always contains the same mass of peptide. Water only changes the concentration and therefore the volume you draw for a given amount. A vial reconstituted with 1 mL and one reconstituted with 3 mL deliver the same total peptide across the vial's life.
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