Peptide Reconstitution Calculator
Enter the mass of peptide in the vial, the volume of diluent added and the amount of peptide each aliquot should contain. The calculator returns the stock concentration in mg/mL and µg/mL, the volume of solution holding that amount in mL and µL, and the number of whole aliquots of that size the vial yields. Use it to plan a reconstitution before the vial is opened; the peptide reconstitution guide covers the bench method itself.
Results
- Concentration
- 2.50 mg/mL
- (2500 µg/mL)
- Volume containing 250 µg
- 0.100 mL
- = 100.0 µL
- Aliquots per vial
- 20
Provided for laboratory calculation convenience only. All compounds sold by Australian Peptide Lab are for in-vitro research use only — not for human or veterinary use.
Reconstitution sets the concentration that every later step inherits, so it is worth calculating before any diluent goes in. The calculator needs three numbers and returns three results.
The formulas
| Result | Formula | Default inputs (5 mg, 2.0 mL, 250 µg) |
|---|---|---|
| Concentration | vial mass (mg) ÷ diluent volume (mL) | 2.50 mg/mL = 2,500 µg/mL |
| Volume holding the aliquot amount | amount (µg) ÷ 1,000 ÷ concentration (mg/mL) | 0.100 mL = 100.0 µL |
| Aliquots per vial | diluent volume ÷ aliquot volume, rounded down | 20 |
Worked examples
| Vial | Diluent | Concentration | Peptide per aliquot | Aliquot volume | Aliquots |
|---|---|---|---|---|---|
| Semax, 5 mg | 1.0 mL | 5.00 mg/mL | 150 µg | 30.0 µL | 33 (33.3 rounded down) |
| Selank, 10 mg | 3.0 mL | 3.33 mg/mL | 250 µg | 75.0 µL | 40 |
| MOTS-c, 10 mg | 2.0 mL | 5.00 mg/mL | 200 µg | 40.0 µL | 50 |
| Epithalon, 50 mg | 5.0 mL | 10.00 mg/mL | 1,000 µg | 100.0 µL | 50 |
| GHK-Cu, 100 mg | 10.0 mL | 10.00 mg/mL | 500 µg | 50.0 µL | 200 |
| Any 5 mg vial | 2.0 mL | 2.50 mg/mL | 20 µg | 8.0 µL | 250 |
The displayed concentration is rounded to two decimal places, but the volumes are calculated from the unrounded value: 10 mg in 3.0 mL shows as 3.33 mg/mL, yet 250 µg still comes out at exactly 75.0 µL.
Choosing the diluent volume
The last row shows the trade-off. Small aliquots of a concentrated stock mean single-digit microlitre volumes, where pipetting error is proportionally largest. A larger diluent volume makes each aliquot easier to measure but lowers the concentration, and dilute peptide solutions lose a larger fraction to container walls, as the reconstitution guide explains. One workable pattern is to keep the stock in the low mg/mL range, store larger aliquots and prepare small amounts by dilution at the point of use with the dilution calculator. Planning single-use aliquots also spares the stock repeated freeze–thaw cycles.
The diluent changes nothing in the arithmetic but matters for the stock. Bacteriostatic water suits a refrigerated stock entered repeatedly, while sterile water adds nothing to an assay vehicle; bacteriostatic water versus sterile water compares the two.
Correcting for net peptide content
The vial field is read as pure peptide. A lyophilised powder also contains counter-ions and water, so the peptide actually present is the fill multiplied by its net peptide content (NPC). Entering the corrected mass changes every result:
| 5 mg vial, 2.0 mL, 250 µg aliquots | Entered mass | Concentration | Aliquot volume | Aliquots |
|---|---|---|---|---|
| Uncorrected | 5 mg | 2.50 mg/mL | 100.0 µL | 20 |
| NPC 80% | 4 mg | 2.00 mg/mL | 125.0 µL | 16 |
Without the correction, each 100 µL aliquot labelled 250 µg holds about 200 µg of peptide.
Blend vials
For a two-peptide vial such as the BPC-157 + TB-500 blend, enter the mass of one component, not the combined fill. A 5 mg + 5 mg vial in 2.0 mL is 2.50 mg/mL of each peptide; entering 10 mg would report 5.00 mg/mL and halve every aliquot volume. When component masses differ, run the calculator once per component with the same diluent volume. The peptide blends guide covers the wider issues.
What the arithmetic leaves out
- Volume added by the powder. Dissolved peptide adds a little to the final volume. Even allowing a generous 1 µL per mg, 5 mg adds at most 5 µL to 2.0 mL (0.25%); 50 mg in 1.0 mL could add up to 50 µL (5%).
- Unrecoverable volume. Liquid left in the vial and lost during transfers reduces the real aliquot count.
- Incomplete dissolution. Undissolved material lowers the true concentration; see reconstitution and the solubility troubleshooting guide.
For storage of the finished aliquots, see the peptide storage guide.
Frequently asked questions
How much diluent should go into the vial?
Work backwards from what the stock has to do. Pick a volume that puts each aliquot comfortably inside a pipette's range and keeps the concentration within the peptide's solubility. Then try a few values here: for a 5 mg vial, 1.0 mL gives 5.00 mg/mL and 2.5 mL gives 2.00 mg/mL. Neither is correct in general; the experiment decides.
Why might fewer aliquots be recovered than the calculator shows?
The count is whole aliquots of the diluent volume, rounded down, and it assumes every microlitre can be recovered. In practice some solution stays on the vial walls and in the dead space at the bottom, and some is lost in each transfer. Plan on fewer than the theoretical figure, especially when aliquots are small.
Does the calculator account for net peptide content?
No. It treats the full vial mass as peptide. To correct, enter the vial mass multiplied by the net peptide content: a 5 mg fill at 80% is entered as 4 mg. Concentrations and aliquot volumes then refer to actual peptide. For APL vials, the batch documentation is available on request.
What is the difference between mg/mL, µg/mL and mcg?
One mg is 1,000 µg, so 2.50 mg/mL and 2,500 µg/mL are the same concentration. "mcg" is another way of writing µg, used where the µ symbol is unavailable. The aliquot field takes µg and the vial field takes mg, so 0.25 mg is entered as 250 in the aliquot field.
How is the result converted to a molar concentration?
Divide mg/mL by the molecular weight in g/mol and multiply by 1,000 to get mM. The molarity calculator does this and the reverse; for a sequence without a listed molecular weight, the peptide molecular weight calculator supplies it.
Related guides
Peptide Reconstitution: A Bench Method for Lyophilised Research Peptides
A bench method for reconstituting lyophilised peptides: equilibration, diluent choice, adding diluent, concentration tables, aliquoting and labelling.
8 min read →Lab TechniqueBacteriostatic Water vs Sterile Water: Choosing a Diluent for In-Vitro Peptide Work
Bacteriostatic vs sterile water for peptide stocks: a comparison table, benzyl alcohol levels carried into assays, vehicle controls and when each fits.
6 min read →Lab TechniquePeptide Storage and Stability: Powder, Solutions and Australian Summer Transit
How research peptides degrade and how to store them: powder vs solution, freeze–thaw, light, humidity and heat during Australian summer transit.
7 min read →Lab TechniquePeptide Blends Explained: Mass vs Molar Ratios, Analysis and Experimental Design
How fixed-ratio co-lyophilised peptide blends work: mass vs molar ratios, analytical challenges, and when separate vials suit experimental design better.
6 min read →More lab tools
Peptide Molarity Calculator
Convert between peptide mass, molecular weight and molar concentration (mM, µM).
Peptide Molecular Weight Calculator
Paste a sequence to get average MW, monoisotopic mass, [M+H]⁺ and molecular formula.
Peptide Dilution Calculator
How much stock solution and diluent to combine for a working concentration.