Peptide Solution Concentration Calculator
Enter your vial content and diluent volume to calculate solution concentration and the transfer volume required for a given assay amount. For in-vitro research use only.
Enter your vial content, diluent volume, and the target peptide mass for your assay. The calculator returns your stock concentration and the transfer volume required.
Total peptide mass on vial label
Total diluent added to vial (mL)
Mass required for assay (mcg)
2.50 mg/mL
2500 mcg/mL
100.0 µL
0.1000 mL
How to use this calculator
- 1Enter the total peptide content of your vial in milligrams (mg). This is the amount printed on the vial label.
- 2Enter the total volume of diluent (PBS, assay buffer, DMSO, or dilute acetic acid as appropriate for your protocol) added to the vial in milliliters (mL). This determines your stock solution concentration.
- 3Enter the peptide mass required for your assay in micrograms (mcg).
- 4The calculator outputs the resulting stock concentration in mcg/mL and the transfer volume in µL required to deliver that mass to your assay well or tube.
- 5Switch to the Reverse tab if you know the transfer volume already used and need to verify the resulting peptide mass.
Research Use Only
This tool is provided for in-vitro laboratory research planning only. All compounds sold by Pure Peptides are strictly for laboratory research use. This calculator does not constitute medical advice and must not be used to guide administration of any substance in humans or animals.
Common diluent volumes
Reconstitution FAQs
Which diluent should I use to reconstitute a lyophilised peptide for in-vitro use?
The appropriate diluent depends on the compound and assay conditions. Aqueous buffer systems such as sterile PBS (pH 7.4) or standard assay buffer are suitable for most peptides. Poorly water-soluble peptides may require initial dissolution in DMSO followed by dilution into aqueous buffer; a typical starting point is 10 mM in DMSO diluted to ≤0.1% DMSO in the final assay volume. Some peptides, particularly those with cysteine residues or basic character, dissolve more readily in dilute acetic acid (0.1–1%). Consult the compound-specific COA and your institutional protocols for guidance.
How do I reconstitute a lyophilised peptide vial for assay use?
Using a calibrated pipette or micropipette, transfer the appropriate volume of your chosen diluent into the vial. Direct the liquid down the inner wall of the vial to minimize mechanical stress on the lyophilised cake. Gently swirl or rotate the vial until the powder is fully dissolved; do not vortex or shake. The resulting stock solution should be clear. If particulates or cloudiness persist, allow the vial to stand for 15–30 minutes and swirl again before use.
How do I prepare working concentrations from a stock solution?
Once your stock solution is prepared, use serial dilution to reach the working concentration required by your assay. For example, a 1 mg/mL (1000 mcg/mL) stock diluted 1:100 into assay buffer gives a 10 mcg/mL working solution. Use the calculator to determine the stock concentration from your vial content and diluent volume, then calculate the dilution factor needed to reach your target assay concentration.
How should I store a reconstituted peptide stock solution?
Prepare only the volume required for your immediate assay where possible. If storing a reconstituted stock, keep it at 2–8 °C and use within the timeframe specified in your institutional protocol for aqueous research reagents. Avoid repeated freeze-thaw cycles, which can lead to peptide aggregation and degradation. The lyophilised powder remaining in the vial should be stored at -20 °C or below.
What concentration should I target for my stock solution?
Target a stock concentration that gives a practical transfer volume for your assay — ideally 1–100 µL per well or tube. Very small transfer volumes (below 1 µL) introduce pipetting error; very large volumes (above the assay volume) are impractical. Use the calculator to test different diluent volumes and find a stock concentration that places your required assay amounts in the 5–50 µL transfer range for accurate pipetting.
Does the diluent volume change the total peptide content of the vial?
No. The total peptide mass is fixed by the vial label weight regardless of how much diluent is added. Adding more diluent lowers the concentration; adding less raises it. The calculator uses this relationship — concentration (mcg/mL) equals total vial mass in mcg divided by diluent volume in mL — to derive all other values.
What if my peptide does not dissolve completely?
Allow the vial to stand at room temperature for 15–30 minutes after adding diluent and swirl gently. If dissolution remains incomplete, try a different diluent: peptides with high hydrophobic content often require initial dissolution in a small volume of DMSO (typically 10 mM) before aqueous dilution; peptides with multiple basic residues may dissolve better in dilute acetic acid (0.1–1%). Do not heat the solution. If issues persist, consult the COA handling notes or contact us.
Need a laboratory diluent?
We stock research-grade bacteriostatic water in 10 mL vials, suitable as a diluent for certain lyophilised peptide compounds in aqueous buffer protocols.
Shop Bacteriostatic Water