Peptide Reconstitution Calculator
Convert a lyophilised vial and a solvent volume into a working concentration, the volume to draw per measured aliquot, and the equivalent graduation on a U-100 laboratory syringe. All figures are arithmetic conversions for laboratory record keeping.
Vial and solvent
Result
- Concentration
- 5 mg/ml
- Volume per draw
- 0.05 ml
- U-100 syringe
- 5 units
- Draws per vial
- 40
5000 mcg/ml
0.5ml U-100 syringe, marked at the calculated draw line.
How reconstitution arithmetic works
A lyophilised research peptide arrives as a dry cake of a known mass, expressed in milligrams. It becomes a measurable solution once a solvent, usually bacteriostatic water, is introduced into the vial. Because the peptide mass is fixed and only the solvent volume varies, every downstream figure follows from three numbers: the mass in the vial, the volume added, and the mass you intend to withdraw in a single aliquot.
The first calculation is concentration, which is simply the mass divided by the volume: concentration = mg ÷ ml. That gives a figure in milligrams per millilitre, and multiplying by 1000 converts it to micrograms per millilitre, which is the more convenient unit when the target aliquot is small.
The second calculation is the volume to withdraw: draw volume = target mass ÷ concentration. Working in consistent units matters here, so a target expressed in micrograms should be divided by 1000 before it is divided by a concentration expressed in milligrams per millilitre. The calculator above handles that conversion with the mcg and mg toggle.
The third calculation converts that volume into a graduation you can actually read on the barrel. A U-100 laboratory syringe is graduated so that a full millilitre spans one hundred marks, so units = draw volume in ml × 100. A 0.3ml syringe therefore reads to 30 units, a 0.5ml syringe to 50, and a 1.0ml syringe to 100. Choosing the smallest barrel that still contains the draw volume gives the finest resolution and the smallest reading error.
Worked example
Take a 10mg vial and add 2ml of bacteriostatic water. Concentration is 10 ÷ 2, which is 5mg/ml, or 5000mcg/ml. For a target aliquot of 250mcg, convert to 0.25mg and divide by the concentration: 0.25 ÷ 5 = 0.05ml. Multiply by 100 and the syringe reads 5 units. The vial contains 10mg, so at 0.25mg per draw it yields 40 measured aliquots.
How much bacteriostatic water to add
There is no single correct solvent volume. More solvent produces a lower concentration and a larger, more readable draw; less solvent concentrates the material and reduces the volume held in the vial. These are the volumes commonly used in laboratory practice as a starting point.
| Vial size | Typical solvent | Resulting concentration |
|---|---|---|
| 2mg | 1ml | 2mg/ml |
| 5mg | 2ml | 2.5mg/ml |
| 10mg | 2ml | 5mg/ml |
| 15mg | 3ml | 5mg/ml |
| 30mg | 3ml | 10mg/ml |
| 50mg | 5ml | 10mg/ml |
Storage after reconstitution
Once a vial is in solution it should be refrigerated at 2 to 8 degrees Celsius, kept away from light, and used within 30 days. Solutions should not be frozen and thawed repeatedly, and the vial should not be shaken, since agitation can degrade peptide structure. Unreconstituted lyophilised powder is far more stable and can be held frozen for long term storage. Always record the reconstitution date, the solvent volume and the resulting concentration on the vial label so the calculation is reproducible later.
Reconstitution calculator FAQ
How do I calculate peptide concentration after reconstitution?
Divide the peptide mass in the vial by the volume of bacteriostatic water added. A 10mg vial reconstituted with 2ml of solvent gives a concentration of 5mg per ml, which is 5000mcg per ml.
How many units on a U-100 syringe is 0.05ml?
A U-100 insulin syringe is graduated so that 1.0ml equals 100 units. Multiply the draw volume in millilitres by 100, so 0.05ml is 5 units and 0.25ml is 25 units.
How much bacteriostatic water should be added to a vial?
Enough solvent to make the target draw volume comfortably readable on the syringe, and no more than the vial can physically hold. Most 5mg to 15mg vials are reconstituted with 1ml to 3ml, and larger 30mg to 50mg vials with 3ml to 5ml.
Does adding more bacteriostatic water change the amount of peptide?
No. The mass of lyophilised peptide in the vial is fixed. Adding more solvent lowers the concentration, so each measured draw contains the same mass only if the draw volume is increased proportionally.
How should reconstituted material be stored?
Reconstituted solutions are stored refrigerated at 2 to 8 degrees Celsius, protected from light, and are typically used within 30 days. Lyophilised powder that has not been reconstituted is far more stable and can be kept frozen for long term storage.