Planning a reconstitution? This free peptide calculator turns your vial size, bacteriostatic water volume and amount per draw into a concentration, a draw volume and an exact number of syringe units. Pick your syringe, choose or type your numbers, and the syringe diagram shows where the plunger should sit. It also works backwards: enter how many units you want to draw and it tells you how much water to add.
Built for laboratory research planning. Not for human or veterinary use.
Peptide calculator
Assumes a U-100 syringe (100 units = 1 mL) and that the final volume equals the water added. For laboratory research planning only. Not medical advice; not for human or veterinary use.
How to use the peptide calculator
- Choose your syringe size: 0.3 mL, 0.5 mL or 1 mL (30, 50 or 100 units on a U-100 syringe).
- Enter the amount of peptide in the vial, in mg. Check the vial label or your certificate of analysis.
- Enter how much bacteriostatic water you plan to add, in mL.
- Enter the amount you want per draw, in mcg or mg.
- Read the result: concentration, draw volume in mL, syringe units, and roughly how many draws one vial gives you.
Not sure how much water to use? Switch to the How much water to add tab, enter the number of syringe units you would like to draw, and the calculator works out the water volume that gets you there.
How peptide reconstitution math works
Reconstitution is just ratio math. Once you know how concentrated the solution is, every other number follows from it. These are the four formulas behind the calculator:
- Concentration (mcg/mL) = peptide in vial (mg) × 1,000 ÷ water added (mL)
- Draw volume (mL) = amount per draw (mcg) ÷ concentration (mcg/mL)
- Syringe units (U-100) = draw volume (mL) × 100
- Draws per vial = peptide in vial (mcg) ÷ amount per draw (mcg)
Worked example
A 5 mg vial reconstituted with 2 mL of bacteriostatic water has a concentration of 5 ÷ 2 = 2.5 mg/mL, or 2,500 mcg/mL. For 250 mcg per draw, the draw volume is 250 ÷ 2,500 = 0.1 mL, which is 10 units on a U-100 syringe. The vial holds 5,000 mcg, so it provides about 20 draws of 250 mcg.
Peptide reconstitution chart
Common vial sizes and water volumes, with the syringe units needed for three typical amounts per draw.
| Vial | Water added | Concentration | 100 mcg draw | 250 mcg draw | 500 mcg draw |
|---|---|---|---|---|---|
| 5 mg | 1 mL | 5 mg/mL | 2 units | 5 units | 10 units |
| 5 mg | 2 mL | 2.5 mg/mL | 4 units | 10 units | 20 units |
| 5 mg | 3 mL | 1.67 mg/mL | 6 units | 15 units | 30 units |
| 10 mg | 1 mL | 10 mg/mL | 1 unit | 2.5 units | 5 units |
| 10 mg | 2 mL | 5 mg/mL | 2 units | 5 units | 10 units |
| 10 mg | 3 mL | 3.33 mg/mL | 3 units | 7.5 units | 15 units |
| 10 mg | 5 mL | 2 mg/mL | 5 units | 12.5 units | 25 units |
| 15 mg | 2 mL | 7.5 mg/mL | 1.3 units | 3.3 units | 6.7 units |
| 15 mg | 3 mL | 5 mg/mL | 2 units | 5 units | 10 units |
| 15 mg | 5 mL | 3 mg/mL | 3.3 units | 8.3 units | 16.7 units |
Reconstitution basics
General laboratory practice for reconstituting a lyophilized peptide:
- Work on a clean surface and wipe the vial stoppers with an alcohol pad.
- Draw the bacteriostatic water into a sterile syringe.
- Add the water slowly, aiming the stream at the inside wall of the vial rather than straight onto the powder.
- Swirl gently until the powder dissolves. Avoid vigorous shaking, which causes foaming and may damage some peptides.
- Label the vial with the date and concentration, and store it as directed for your material (usually refrigerated and protected from light).
These notes are general information for laboratory research only. Always follow the handling guidance that comes with your material.
Frequently asked questions
What is peptide reconstitution?
Most research peptides are supplied as a freeze-dried (lyophilized) powder. Reconstitution means dissolving that powder in a sterile solvent, usually bacteriostatic water, so you end up with a solution of known concentration that can be measured out by volume.
How do I calculate peptide concentration?
Divide the amount of peptide in the vial by the volume of water you add. A 5 mg vial reconstituted with 2 mL of water gives 5 mg ÷ 2 mL = 2.5 mg/mL, which is the same as 2,500 mcg/mL.
How many units is 0.1 mL on a U-100 syringe?
A U-100 syringe has 100 units per 1 mL, so 0.1 mL is 10 units, 0.05 mL is 5 units and 0.25 mL is 25 units. Multiply the draw volume in mL by 100 to get units.
What size syringe should I use?
Use the smallest syringe that can hold the volume you need to draw. A 0.3 mL syringe holds 30 units, a 0.5 mL syringe holds 50 units and a 1 mL syringe holds 100 units. Smaller syringes have finer markings, which makes small volumes easier to read.
What is bacteriostatic water?
Bacteriostatic water is sterile water containing 0.9% benzyl alcohol as a preservative. The preservative limits bacterial growth, which is why it is the usual choice when a vial will be accessed more than once in a laboratory setting.
How much bacteriostatic water should I add?
There is no single correct amount. Adding more water gives a lower concentration and a larger draw volume, which is easier to measure accurately; adding less water gives a stronger solution and a smaller draw. A practical target is a draw volume that lands comfortably on a clearly marked part of your syringe. The "How much water to add" tab of the calculator works this out for you.
Does the powder change the final volume?
Slightly, but a few milligrams of lyophilized peptide add a negligible amount of volume, so this calculator treats the final volume as equal to the water you add. That is the standard assumption for reconstitution math.
How should reconstituted peptides be stored?
As a general laboratory practice, reconstituted solutions are kept refrigerated (around 2–8 °C), protected from light and not repeatedly frozen and thawed. Stability differs between compounds, so follow the guidance supplied with your material and its certificate of analysis.
Is this calculator for human use?
No. This tool is provided for laboratory research planning and general arithmetic only. PepClub.Shop products are for laboratory and research use only, are not for human or veterinary use, and nothing on this page is medical advice.
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Research peptides from PepClub.Shop
PepClub.Shop supplies research-use-only peptides, bacteriostatic water and lab supplies to qualified adult researchers, laboratories and institutions. Accounts are verified, certificates of analysis are available on request, and orders ship by USPS Ground Advantage.