Peptide calculator.

The relationship between mg of peptide, mL of bacteriostatic water, and dose volume is one division and one multiplication. The shortcut:

1. Concentration (mg/mL) = peptide mg in vial ÷ bacteriostatic water mL
2. Dose volume (mL) = target dose mg ÷ concentration
3. Insulin-syringe units (IU) = dose volume × 100, since 1 IU on a U-100 insulin syringe = 0.01 mL

Most research protocols quote doses in mcg or mg; the calculator above accepts both. The insulin-syringe convention (1 IU = 0.01 mL on a U-100 syringe) is universal across research and clinical practice.

Worked example

A 5 mg vial reconstituted with 2 mL bacteriostatic water gives a concentration of 2.5 mg/mL. To dose 250 mcg (0.25 mg), the dose volume is 0.1 mL — which is 10 IU on a U-100 insulin syringe. The vial yields 5 mg ÷ 0.25 mg = 20 doses.

Converting insulin syringe units to mg

A U-100 insulin syringe holds 100 units in 1 mL, so 1 unit = 0.01 mL. Converting units to mg requires the reconstituted concentration. The same 10-unit draw from a 5 mg vial reconstituted in 1 mL of BAC water (5 mg/mL) instead delivers 0.5 mg. Always recalculate when you change the reconstitution volume — units alone are not a dose.

Why bacteriostatic water

Bacteriostatic water contains 0.9% benzyl alcohol as a preservative, which prevents bacterial growth across multiple draws from the same vial. Sterile (non-bacteriostatic) water is single-use and not appropriate for multi-dose reconstitution.

Storage after reconstitution

Most peptides are stable for 14–30 days at refrigerator temperature (2–8°C) post-reconstitution, protected from light. Longer storage requires freezing in single-dose aliquots to avoid freeze-thaw cycles. Compound-specific stability data varies — see our reconstitution guide for detail.