Use this free peptide reconstitution calculator to work out the concentration of a reconstituted vial, how much to draw into a U-100 insulin syringe to reach a target amount, and how many draws a vial yields — instantly, as you type.
Research reference only. This tool does the reconstitution arithmetic for laboratory/research handling — it is not medical advice, not a dosing recommendation, and not intended for human use. Most peptides are not FDA-approved. Verify every figure and consult a licensed professional.
mg
mL
—units to draw
Enter your vial, water, and dose to see the draw.
—Concentration (mg/mL)
—Concentration (mcg/mL)
—Volume per dose (mL)
—Doses per vial
—mcg per unit
—Syringe used
How the math works
1
Find the concentration
Divide the peptide amount by the water you added: concentration = mg ÷ mL. Adding more water does not change how much peptide is in the vial — it only makes the solution more dilute, so each unit carries less.
2
Convert the dose to units
Divide your dose by the concentration to get the volume, then multiply by 100: units = (dose ÷ concentration) × 100. On a U-100 insulin syringe, 100 units = 1 mL, so 1 unit = 0.01 mL.
Frequently asked questions
What does “reconstitute” mean?
Research peptides ship as a freeze-dried (lyophilized) powder. Reconstituting means adding a sterile liquid — usually bacteriostatic water — to dissolve the powder into a measurable solution. Nothing is created or lost; you are only turning a solid into a liquid of a known concentration.
Does adding more water change the dose or potency?
No. The vial always holds the same milligrams of peptide. More water spreads that same amount across more volume, so each 0.01 mL unit contains less peptide and you draw more units for the same dose. Less water does the opposite. Potency per milligram is unchanged.
What is a “unit” on a U-100 insulin syringe?
A U-100 syringe is graduated so that 100 units equals 1 mL — each unit is 0.01 mL. It is the most common syringe for small subcutaneous volumes, which is why this calculator expresses the draw in units rather than fractions of a millilitre.
Bacteriostatic water vs. sterile water — which is used?
Bacteriostatic water contains a small amount of benzyl alcohol that inhibits bacterial growth, so a multi-use vial stays usable for longer once opened. Plain sterile water has no preservative and is generally intended for single use. This is general reference information, not a directive — follow the guidance for your specific material and setting.
How do I read the units on my syringe?
Hold the syringe with the needle up and draw liquid until the top edge of the rubber plunger tip lines up with the target unit marking. The numbers increase from the needle end toward the plunger. Draw slowly and tap out air bubbles.
What if my dose needs more units than the syringe holds?
A draw that overflows the syringe means the solution is too dilute. Use less bacteriostatic water next time so the vial is more concentrated — each unit then carries more peptide, so the same dose fits in fewer units — or simply step up to a larger syringe. This calculator flags when a draw exceeds the selected syringe, and the “Auto” setting always picks the smallest syringe that fits.
How long does a reconstituted vial last?
Once mixed, peptides are generally kept refrigerated and protected from light, and many degrade over a matter of weeks. Exact stability varies widely by peptide and storage conditions. Treat any figure here as general reference and follow the storage guidance for your specific compound.
How do I convert between mcg and mg?
1 mg = 1000 mcg. So 250 mcg = 0.25 mg, and 2 mg = 2000 mcg. Use the mcg/mg toggle above so you can enter your dose in whatever unit the source describes.
This calculator is for educational reference only. Figures depend entirely on your inputs; double-check them against your material. Not medical advice.
