Peptide Calculator
Free peptide reconstitution and dosage calculator. Enter your vial size, the amount of bacteriostatic water you are adding, and your dose. The calculator shows the exact volume to draw into your syringe, in units.
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How to use the peptide calculator
Following these four steps gives you the right amount of water to add to your peptide powder and the exact volume to draw for your dose.
Step 1: Choose your syringe size
Select the total volume of the insulin syringe you are using. Most people use a 0.3 mL syringe, which is marked to 30 units. The calculator uses this to convert your dose into syringe units and to warn you if a dose will not fit.
Step 2: Enter the peptide amount in your vial
Enter the total milligrams of peptide in the vial before mixing. Vials commonly come in 1 mg, 2 mg, 5 mg, 10 mg, or 15 mg. If your vial is a size not listed, choose Other and type it in.
Step 3: Enter the bacteriostatic water you are adding
Enter the volume of bacteriostatic water in milliliters. This determines the concentration of the finished solution. More water produces a weaker concentration and a larger draw volume. Less water produces a stronger concentration and a smaller draw volume.
Step 4: Enter your dose and read the meter
Enter the dose you plan to inject and select mcg or mg. The calculator displays the volume to draw in both milliliters and syringe units, and the meter fills to show roughly where to stop pulling the plunger. On any insulin syringe, 1 mL equals 100 units.
Worked example
- Vial: 1 mg of peptide
- Water added: 2 mL bacteriostatic water
- Dose: 250 mcg per injection
Concentration: 1 mg equals 1000 mcg. 1000 mcg dissolved in 2 mL gives 500 mcg per mL.
Volume to draw: 250 mcg divided by 500 mcg per mL equals 0.5 mL.
On the syringe: 0.5 mL equals 50 units.
Reconstitution basics
Reconstitution is the process of dissolving a lyophilized peptide powder into a liquid so it can be measured and injected. Bacteriostatic water is used because it contains a small amount of benzyl alcohol, which allows the vial to be entered more than once over a period of time.
The powder amount and the water amount together set the concentration. Concentration in mcg per mL equals the vial amount in mcg divided by the water volume in mL. Once you know the concentration, the draw volume is your dose divided by that concentration.
Common peptide vial sizes and concentrations
Vial sizes vary by pharmacy and by compound. The table below shows typical vial sizes and the concentration you get at a common reconstitution volume. Always confirm the amount printed on your own vial before mixing, and follow the instructions from your prescribing provider.
| Peptide | Common vial size | Water added | Resulting concentration |
|---|---|---|---|
| Pentadeca Arginate (PDA), also known as BPC-157 | 5 mg | 2 mL | 2,500 mcg per mL |
| TB-500 | 5 mg | 2 mL | 2,500 mcg per mL |
| PDA and TB-500 blend | 10 mg total | 2 mL | 5,000 mcg per mL |
| CJC-1295 and ipamorelin blend | 6 mg and 6 mg | 3 mL | 2,000 mcg per mL of each |
| Sermorelin | 5 mg | 2 mL | 2,500 mcg per mL |
| Tesamorelin | 5 mg | 2 mL | 2,500 mcg per mL |
| Hexarelin | 6 mg | 3 mL | 2,000 mcg per mL |
| PT-141 | 10 mg | 2 mL | 5,000 mcg per mL |
| GHK-Cu | 50 mg | 5 mL | 10 mg per mL |
| Semaglutide | 5 mg | 2 mL | 2.5 mg per mL |
| Tirzepatide | 10 mg | 2 mL | 5 mg per mL |
Concentrations above are arithmetic, not dosing guidance. Enter your own vial size and water volume in the calculator to get the draw volume for the dose your provider prescribed.
Frequently asked questions
How much bacteriostatic water should I add to my vial?
There is no single correct amount. The water volume sets the concentration, and the concentration determines how many units you draw. Many people choose a volume that puts their dose somewhere in the middle of the syringe barrel, which is easier to measure accurately than a very small draw. If your provider specified a reconstitution volume, use that.
Why does my dose show as units instead of milliliters?
Insulin syringes are marked in units rather than milliliters. On any insulin syringe, 100 units equals 1 mL, so 50 units is 0.5 mL and 10 units is 0.1 mL. The calculator shows both so you can read either marking.
Can I use this calculator for semaglutide and tirzepatide?
Yes. GLP-1 medications are usually dosed in milligrams rather than micrograms, so switch the dose unit to mg before entering your number. The math is the same. If you want the full walkthrough, see our guide on mixing and drawing up semaglutide.
What does the calculator do if my dose will not fit in the syringe?
It shows a warning along with the number of units the dose actually requires. From there you have two options: reconstitute with less bacteriostatic water to make a stronger solution, or use a larger syringe.
Is bacteriostatic water the same as sterile water?
No. Bacteriostatic water contains a small amount of benzyl alcohol, which allows the vial to be entered more than once over a period of time. Sterile water contains no preservative, and the difference between the two matters for multi-use vials. Use whichever your provider or pharmacy specifies.
Does the calculator account for the powder taking up volume?
No, and in practice this is not a meaningful factor. The lyophilized powder in a typical peptide vial occupies a negligible volume compared with the milliliters of water being added, so the concentration is calculated from the water volume alone. This is the standard approach.
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Browse Our Peptide Menu →This calculator is provided for educational purposes and is not medical advice. It is not intended to diagnose, treat, cure, or prevent any disease, and it is not a substitute for a consultation with your physician. Always follow the dosing instructions provided by your prescribing provider.