Peptide Calculator

Quickly calculate concentration and laboratory aliquot volume for research samples.

Peptide in vial

Bacteriostatic water added

Concentration 1.667 mg/mL

Target dose per injection

Syringe size

50-unit (0.5 mL): 1-unit marks. A good middle ground for draws of roughly 15–45 units.

Calculated syringe draw

3 units

Scale: 0–50 units · Calculated draw: 3 units

Worked Example: Reconstituting a 5 mg Vial

Suppose you have a 5 mg vial of a research peptide such as BPC-157 and you add 2 mL of bacteriostatic water. The concentration is 5 mg ÷ 2 mL = 2.5 mg/mL, or 2500 mcg/mL. Each insulin unit (0.01 mL) therefore contains 25 mcg of peptide.

If your protocol calls for a 250 mcg dose, the draw volume is 250 mcg ÷ 2500 mcg/mL = 0.1 mL, which is 10 units on the U-100 scale. The 5 mg vial holds 5000 mcg ÷ 250 mcg = 20 full doses. Reconstitute the same 5 mg vial with 1 mL of water instead and the concentration doubles to 5 mg/mL, so the same 250 mcg dose draws to just 5 units. Reconstitute with 3 mL and the concentration falls to about 1.67 mg/mL, pushing the same dose out to roughly 15 units. Nothing about the peptide changed — only the water volume — yet the number you read on the syringe moved substantially. This is exactly the relationship the peptide calculator makes visible, so you can choose a concentration that lands your dose on a clean, easy-to-read mark.

Frequently Asked Questions

How much bacteriostatic water should I add to a peptide vial?

There is no single correct volume — the amount of water sets the concentration, not the dose. Adding more bacteriostatic water gives a larger, easier-to-measure draw per dose; adding less gives a higher concentration and a smaller draw. Enter your vial size and target dose into the calculator and adjust the water until the draw lands on a convenient syringe mark. Common choices are 1 mL, 2 mL, and 3 mL.

How do I calculate a peptide dose in units?

Divide your desired dose by the solution's concentration to get the draw volume in milliliters, then multiply by 100 to get units on a U-100 insulin syringe. For example, a 250 mcg dose from a 2.5 mg/mL solution is 0.1 mL, or 10 units. The peptide calculator runs this conversion automatically as soon as you enter the dose.

What syringe size is best for peptides?

Match the barrel to your draw. A 30-unit (0.3 mL) syringe has the finest marks and is the most accurate for small doses; a 50-unit (0.5 mL) syringe suits mid-range draws; and a 100-unit (1 mL) syringe fits the largest draws. All three use the same U-100 scale, so the unit number is identical — only the precision differs. The calculator recommends the smallest barrel that fits your dose.

How long does a reconstituted peptide vial last?

Once reconstituted, a peptide solution is far less stable than the dry powder and should be kept refrigerated and away from light. Reconstituted research peptides are generally used within a few weeks, whereas lyophilized powder can remain stable in cold storage for many months. Always follow the storage guidance for your specific compound.

Can I use sterile water instead of bacteriostatic water?

Sterile water contains no preservative, so a vial reconstituted with it offers no protection against microbial growth once opened and is best suited to single use. Bacteriostatic water contains 0.9% benzyl alcohol, which suppresses microbial growth and makes multi-dose use over a vial's life more practical. The calculator's math is identical for either diluent.

How do I convert mcg to mL?

You cannot convert micrograms to milliliters without knowing the concentration, because micrograms measure mass and milliliters measure volume. Once the peptide is reconstituted, divide the dose in micrograms by the concentration in mcg/mL to get the volume in milliliters. This is exactly the calculation the peptide calculator performs for you.

For research and educational use only. This peptide calculator and the information above support laboratory and educational reference. Research peptides are not approved for human consumption. Always confirm every calculation independently and consult a qualified professional before making decisions.