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Peptide Reconstitution Calculator

Turn vial size, water, and target dose into the exact units to draw on an insulin syringe.

Picking a peptide fills typical starting values. Always match your own vial label.

Draw on the syringe
10 units
= 0.1 mL on a U-100 insulin syringe
0100
Concentration2.5 mg/mL
Per unit25 mcg/unit
Doses per vialabout 20

Estimate for educational use, not medical advice or a dosing recommendation. Verify against your vial label and a qualified professional.

Worked examples

5 mg vial, 2 mL water, 250 mcg dose
Concentration = 5 ÷ 2 = 2.5 mg/mL. 250 mcg = 0.25 mg, so volume = 0.25 ÷ 2.5 = 0.1 mL = 10 units on a U-100 syringe. The vial holds about 20 doses.
10 mg vial, 1 mL water, 500 mcg dose
Concentration = 10 ÷ 1 = 10 mg/mL. 500 mcg = 0.5 mg, so volume = 0.5 ÷ 10 = 0.05 mL = 5 units. About 20 doses per vial.
Tirzepatide 30 mg vial, 2 mL water, 2.5 mg dose
Concentration = 30 ÷ 2 = 15 mg/mL. Volume = 2.5 ÷ 15 = 0.167 mL ≈ 16.7 units. The vial holds about 12 doses of 2.5 mg.
Semaglutide 5 mg vial, 2 mL water, 0.25 mg dose
Concentration = 5 ÷ 2 = 2.5 mg/mL. Volume = 0.25 ÷ 2.5 = 0.1 mL = 10 units. The vial holds about 20 starter doses.

How the peptide reconstitution calculator works

Reconstitution means adding liquid, almost always bacteriostatic water, to a freeze-dried (lyophilized) peptide so it can be measured and drawn into a syringe. The math is short and always the same, whatever the peptide. This tool runs it for you and draws the exact fill line on an insulin syringe, but the whole thing is three steps you can check by hand.

Step 1: concentration

The peptide dissolves evenly into the water you add, so the concentration is simply the amount in the vial divided by the water volume:

Concentration (mg/mL) = vial amount (mg) ÷ water added (mL)

A 5 mg vial with 2 mL of water is 2.5 mg/mL. The same 5 mg vial with only 1 mL of water is 5 mg/mL, twice as concentrated. The water volume is a choice you make; it does not change how much peptide is in the vial, only how spread out it is.

Step 2: volume per dose

Now convert your target dose into a volume. Keep the units consistent by turning micrograms into milligrams first (divide mcg by 1,000), then divide by the concentration:

Volume (mL) = dose (mg) ÷ concentration (mg/mL)

For a 250 mcg (0.25 mg) dose at 2.5 mg/mL, that is 0.25 ÷ 2.5 = 0.1 mL.

Step 3: units on the syringe

Insulin syringes are almost always U-100, meaning 100 units equal 1 mL. So multiply the volume in millilitres by 100:

Units = volume (mL) × 100

0.1 mL becomes 10 units. That is the mark you draw the plunger back to. The calculator also reports the concentration in micrograms per unit, so you can see at a glance how much peptide each unit carries.

A shortcut worth knowing

Because units and micrograms per unit are both fixed once you choose your water volume, you can read doses straight off the syringe. In the 5 mg + 2 mL example, every unit is 25 mcg, so 10 units is 250 mcg, 20 units is 500 mcg, and so on. Choosing a water volume that makes your usual dose land on a round number of units is the single best way to avoid measuring mistakes.

Choosing your water volume

There is no “correct” amount of bacteriostatic water. More water gives a dilute solution and a larger, easier-to-read number of units per dose. Less water concentrates the peptide into fewer units, which can be harder to measure precisely on a small syringe. Pick the volume that puts your dose at a clean unit count and fits comfortably inside your syringe’s capacity. The calculator warns you if the dose you entered would not fit in the syringe you selected.

Doses per vial

Finally, to see how long a vial lasts, divide the total peptide by your dose per injection in the same units:

Doses per vial = vial amount ÷ dose per injection

A 10 mg vial at 500 mcg (0.5 mg) per dose is 10 ÷ 0.5 = 20 doses. Water volume has no effect on this count.

Important safety note

This is a calculator, not a clinician. It performs the reconstitution arithmetic and nothing more: it does not recommend a peptide, a dose, a frequency, or a protocol, and it cannot tell you whether anything is appropriate or safe for you. Many peptides are sold “for research use only” and are not approved for human use. Reconstituting and injecting any substance carries real risks of contamination, dosing error, and harm.

Treat every result as an estimate for educational purposes only, not medical advice. Verify the peptide amount against your own vial label, double-check the math, talk to a licensed medical professional before acting, and follow all laws that apply to the product you have.

Frequently asked questions

How do I calculate peptide reconstitution?
Divide the peptide amount in the vial (mg) by the volume of bacteriostatic water you add (mL) to get the concentration in mg/mL. Then divide your target dose (in mg) by that concentration to get the injection volume in mL, and multiply by 100 to get units on a standard U-100 insulin syringe. The calculator does all three steps and shows the exact fill line.
How much bacteriostatic water should I add to a peptide vial?
There is no single correct amount; the water volume only sets the concentration, not the total dose you receive. Common choices are 1 mL or 2 mL per vial. More water makes the solution more dilute, so you draw more units for the same dose, which can be easier to measure accurately. Less water concentrates it into fewer units. Pick a volume that puts your usual dose at a round, easy-to-read number of units.
What does one unit on an insulin syringe mean?
A standard U-100 insulin syringe is marked so that 100 units equal 1 mL. So 1 unit is 0.01 mL. Units measure volume, not the amount of peptide. The amount of peptide in each unit depends entirely on your concentration, which is why the same 10 units can be 250 mcg from one vial and 500 mcg from another.
Why bacteriostatic water and not regular water?
Bacteriostatic water is sterile water with about 0.9% benzyl alcohol added as a preservative. The benzyl alcohol slows bacterial growth, which is what lets a reconstituted vial be stored and used across multiple doses over several weeks in the fridge. Sterile water without preservative is intended for single use.
How many doses will one vial give me?
Divide the total peptide in the vial by your dose per injection, keeping the units the same. A 5 mg vial dosed at 250 mcg (0.25 mg) gives 5 ÷ 0.25 = 20 doses. The water volume does not change this number; it only changes how many units each dose measures out to.
Is this peptide calculator medical advice?
No. It is an educational math tool that converts vial size, water, and dose into syringe units. It does not recommend a peptide, a dose, or a protocol, and it cannot tell you what is safe for you. Reconstituting and injecting substances carries real risk. Talk to a licensed medical professional, and follow all applicable laws for the product you have.

Related tools

Tirzepatide Reconstitution CalculatorConvert a tirzepatide vial, water, and dose into exact insulin-syringe units.Semaglutide Reconstitution CalculatorConvert a semaglutide vial, water, and dose into exact insulin-syringe units.Retatrutide Reconstitution CalculatorConvert a retatrutide vial, water, and dose into exact insulin-syringe units.BPC-157 Reconstitution CalculatorConvert a BPC-157 vial, water, and microgram dose into exact insulin-syringe units.

Last updated: 2026-07-11