Work out the concentration of a reconstituted research peptide, the volume corresponding to a given quantity, and how many aliquots a vial yields. Pick a compound below to load its vial size, or enter your own figures. Provided as a laboratory reference for research use only.
How the calculation works
There are only two steps, and doing them by hand is a useful check on any calculator:
- Concentration. Divide the peptide mass in the vial by the volume of bacteriostatic water added. A 10 mg vial reconstituted with 2 mL gives 5 mg/mL, or 5,000 mcg/mL.
- Volume. Divide the amount you want by that concentration. 250 mcg at 5,000 mcg/mL is 0.05 mL.
Reading the result on a U-100 syringe
This is where most errors happen. A U-100 insulin syringe is marked in units, where 100 units = 1 mL. That ratio does not change with the size of the barrel: a 0.3 mL, 0.5 mL and 1 mL U-100 syringe all use the same scale, they simply stop at 30, 50 and 100 units respectively.
So a 0.5 mL syringe labelled to 50 units is not “half units” — 50 units on it is still 0.5 mL. Converting is therefore always the same: units = millilitres × 100. The calculator above shows both.
Common reconstitution volumes
Reference values for the vial sizes we supply. Concentrations are exact; adjust the water volume to suit the resolution you need on your syringe.
| Vial | Water added | Concentration | 250 mcg equals |
|---|---|---|---|
| 10 mg | 1 mL | 10,000 mcg/mL | 0.025 mL · 2.5 units |
| 10 mg | 2 mL | 5,000 mcg/mL | 0.05 mL · 5 units |
| 20 mg | 2 mL | 10,000 mcg/mL | 0.025 mL · 2.5 units |
| 20 mg | 3 mL | 6,667 mcg/mL | 0.038 mL · 3.8 units |
| 50 mg | 3 mL | 16,667 mcg/mL | 0.015 mL · 1.5 units |
| 80 mg | 3 mL | 26,667 mcg/mL | 0.009 mL · 0.9 units |
A practical note: if your figure comes out below about 2 units, the graduation on a U-100 syringe is too coarse to measure it reliably. Reconstituting with more water lowers the concentration and moves the measurement into a readable part of the scale.
Why bacteriostatic water rather than sterile water
Bacteriostatic water contains 0.9% benzyl alcohol as a preservative, which inhibits microbial growth and allows a vial to be entered more than once. Plain sterile water has no preservative and is single-use once broached. If a vial will be drawn from repeatedly, bacteriostatic water is the appropriate diluent — this is covered in more depth in our Reconstitution & Storage guide.
We supply bacteriostatic water in 3 mL vials alongside the full research peptide range.
Handling notes
- Add the diluent slowly down the inside wall of the vial rather than directly onto the lyophilised cake.
- Swirl gently until dissolved. Do not vortex or shake vigorously.
- Store reconstituted solution at 4 °C and avoid repeated freeze-thaw cycles.
- Label the vial with the preparation date and resulting concentration.
Always confirm calculations independently before use. This tool does not account for compound-specific stability, peptide salt content or residual moisture, all of which affect the true peptide mass in a vial — defer to your Certificate of Analysis for exact figures. Supplied for in vitro laboratory research use only. Not for human or veterinary use.