Peptide Reconstitution Calculator
A free peptide reconstitution calculator for laboratory preparation. Enter the peptide amount in the vial and the volume of bacteriostatic water added to get the concentration in mg/mL and the matching volume for any amount you need.
How to use this calculator
Enter the total amount of peptide in your vial (e.g. 5mg).
Enter how much BAC water you added to reconstitute (e.g. 2mL).
Enter the amount of peptide your protocol requires (e.g. 0.5mg).
The tool returns the concentration and the matching volume in mL.
All calculations are provided as a laboratory reference only. Products supplied by Just Peptides are for research use only and are not for human or animal consumption.
How the peptide reconstitution calculation works
Reconstitution is the step where a lyophilised (freeze-dried) peptide is dissolved in a diluent, usually bacteriostatic water, so it can be measured accurately. Two formulas cover it.
Concentration (mg/mL) = peptide in vial (mg) ÷ bacteriostatic water added (mL)
Volume required (mL) = amount required (mg) ÷ concentration (mg/mL)
Worked example
A 10mg vial is reconstituted with 2mL of bacteriostatic water:
- Concentration = 10 ÷ 2 = 5 mg/mL
- For 0.5mg of peptide: 0.5 ÷ 5 = 0.1 mL
The calculator above runs both steps for you. Changing the amount of water changes the concentration, not the total amount of peptide in the vial.
Reconstitution reference table
Concentration in mg/mL for common vial sizes and water volumes:
| Vial | + 1 mL | + 2 mL | + 3 mL | + 5 mL |
|---|---|---|---|---|
| 5 mg | 5.00 | 2.50 | 1.67 | 1.00 |
| 10 mg | 10.00 | 5.00 | 3.33 | 2.00 |
| 20 mg | 20.00 | 10.00 | 6.67 | 4.00 |
| 30 mg | 30.00 | 15.00 | 10.00 | 6.00 |
| 50 mg | 50.00 | 25.00 | 16.67 | 10.00 |
Less water gives a higher concentration and a smaller volume per measurement. More water gives a lower concentration, which can make small amounts easier to measure accurately.
Before you reconstitute
- Check the vial contents. Use the amount printed on the label and on the Certificate of Analysis, not an assumed amount. Every batch we supply has a COA on our Quality & Lab Results page.
- Use bacteriostatic water. It is the standard diluent for lyophilised peptides in laboratory work. We stock it here: BAC Water 3ml.
- Add the diluent slowly. Run it down the inside wall of the vial rather than directly onto the powder, and let it dissolve without shaking.
- Record what you used. Note the vial amount, diluent volume and resulting concentration, so later calculations match the same batch.
- Storage. Lyophilised vials are generally stored cool, dry and away from light. Once reconstituted, peptides are typically refrigerated at 2–8°C and used within the period stated in the product documentation.
Frequently asked questions
How do I calculate peptide concentration?
Divide the amount of peptide in the vial (mg) by the volume of bacteriostatic water added (mL). A 10mg vial with 2mL of water gives 5 mg/mL.
How do I work out the volume for a specific amount?
Divide the amount you need (mg) by the concentration (mg/mL). At 5 mg/mL, 0.5mg sits in 0.1 mL.
What is bacteriostatic water?
Sterile water containing a small amount of benzyl alcohol, which limits bacterial growth. It is the standard diluent used to reconstitute lyophilised research peptides.
How much bacteriostatic water should I add to a vial?
There is no single answer. It depends on the concentration your protocol calls for. 1–3 mL is common for 5–10mg vials. The reference table above shows what each combination produces.
Does this calculator provide dosing advice?
No. It performs reconstitution arithmetic for laboratory preparation only. It does not provide medical, dosing or usage guidance, and all products are for research use only.
Where can I check the purity of a batch?
Each batch is supplied with a Certificate of Analysis showing HPLC purity. These are published on our Quality & Lab Results page.
Browse our research peptides, all dispatched from Australian stock with a Certificate of Analysis for every batch.
