Peptide Reconstitution Calculator

How to use this calculator

Reconstitution is the process of dissolving a lyophilized (freeze-dried) peptide into bacteriostatic water before use. The math determines how much peptide you have in each unit of liquid.

The standard formula: concentration (mcg/mL) = vial mass (mg) × 1000 ÷ BAC water volume (mL).

For example, a 5 mg vial reconstituted with 2 mL of bacteriostatic water yields 2,500 mcg/mL (5 × 1000 ÷ 2). On a U-100 insulin syringe (which holds 1 mL across 100 IU marks), that's 25 mcg per IU mark.

Common vial and BAC water combinations

| Vial Size | BAC Water | Concentration (mcg/mL) | Per IU (U-100) | |---|---|---|---| | 2 mg | 1 mL | 2,000 | 20 mcg | | 2 mg | 2 mL | 1,000 | 10 mcg | | 5 mg | 1 mL | 5,000 | 50 mcg | | 5 mg | 2 mL | 2,500 | 25 mcg | | 5 mg | 3 mL | 1,667 | 16.7 mcg | | 10 mg | 2 mL | 5,000 | 50 mcg | | 10 mg | 3 mL | 3,333 | 33.3 mcg | | 10 mg | 5 mL | 2,000 | 20 mcg | | 15 mg | 3 mL | 5,000 | 50 mcg | | 15 mg | 5 mL | 3,000 | 30 mcg | | 20 mg | 5 mL | 4,000 | 40 mcg |

What bacteriostatic water is

Bacteriostatic water (BAC water) is sterile water containing 0.9% benzyl alcohol as a preservative. The preservative prevents bacterial growth, allowing the same vial to be used multiple times after reconstitution. Read our full guide to bacteriostatic water.

Important storage notes

• Lyophilized (unmixed) vials store refrigerated (2-8°C) away from light. Most peptides are stable for 12-24 months in this state.
• Reconstituted solutions store refrigerated. Stability is typically 30 days, though it varies by compound.
• Frozen aliquots are an option for longer-term storage. Avoid multiple freeze-thaw cycles.

For full procedural details, see our complete reconstitution guide.