Peptide Reconstitution Calculator
Enter the vial mass, the volume of bacteriostatic (BAC) water added, and the target amount per administration in your research protocol. The calculator returns concentration in mcg/mL, the draw in mL and U-100 insulin syringe units, and how many doses the vial contains. Same math as any mass dissolved in any solvent: concentration = mass ÷ volume.
For laboratory research calculations only. Verify all arithmetic independently — vial contents include water and counterions, so exact quantitative work applies the net peptide content correction from the batch certificate of analysis.
Common vial setups
These are starting points for the arithmetic, not research protocols. Click a row to pre-fill the calculator. Research vials are commonly sold as 5 mg or 10 mg.
How much BAC water to add
For a 5 mg vial, 2 mL of BAC water gives 2,500 mcg/mL, so a 250 mcg aliquot is a 10-unit draw. Concentration is vial mass divided by BAC water volume. More water means a more dilute solution and a larger (easier to read) syringe draw for the same aliquot. Standard research vials hold about 3 mL; volumes above that need a larger vessel.
| Vial | BAC water | Concentration | Open calculator |
|---|---|---|---|
| 5 mg | 1 mL | 5 mg/mL (5,000 mcg/mL) | Open |
| 5 mg | 2 mL | 2.5 mg/mL (2,500 mcg/mL) | Open |
| 5 mg | 3 mL | 1.67 mg/mL (1,666.7 mcg/mL) | Open |
| 10 mg | 1 mL | 10 mg/mL (10,000 mcg/mL) | Open |
| 10 mg | 2 mL | 5 mg/mL (5,000 mcg/mL) | Open |
| 10 mg | 3 mL | 3.33 mg/mL (3,333.3 mcg/mL) | Open |
| 15 mg | 1 mL | 15 mg/mL (15,000 mcg/mL) | Open |
| 15 mg | 2 mL | 7.5 mg/mL (7,500 mcg/mL) | Open |
| 15 mg | 3 mL | 5 mg/mL (5,000 mcg/mL) | Open |
Each row links with a 250 mcg aliquot so the rows are comparable. On the three most concentrated rows (10 mg in 1 mL, 15 mg in 1 mL, 15 mg in 2 mL) that aliquot lands under 5 units and the calculator will flag it. That is the case for adding more BAC water.
U-100 syringe units for common aliquots
On a U-100 insulin syringe, 100 units = 1 mL, so 1 unit = 0.01 mL. Draws under about 5 units are hard to read accurately; add more BAC water or pick a larger aliquot. Figures below assume a 1 mL (100-unit) syringe.
5 mg vial + 2 mL BAC water (2,500 mcg/mL)
| Aliquot | Draw | U-100 units | Open |
|---|---|---|---|
| 100 mcg | 0.04 mL | 4 units | Open |
| 250 mcg | 0.1 mL | 10 units | Open |
| 500 mcg | 0.2 mL | 20 units | Open |
10 mg vial + 2 mL BAC water (5,000 mcg/mL)
| Aliquot | Draw | U-100 units | Open |
|---|---|---|---|
| 100 mcg | 0.02 mL | 2 units | Open |
| 250 mcg | 0.05 mL | 5 units | Open |
| 500 mcg | 0.1 mL | 10 units | Open |
Several of these draws sit under 5 units; the calculator will warn, and the 3 mL rows in the chart above dilute enough to fix it.
BAC water calculator
If the vial is still dry, the useful question is not "what concentration did I make" but "how much BAC water do I add so this aliquot lands on a syringe mark." Use Target syringe units mode above, or this pre-filled link. It runs the same identities in reverse:
diluent (mL) = vial mass (mcg) × target draw (mL) ÷ target amount (mcg)
Example: 5 mg vial, 250 mcg aliquot, 10-unit (0.1 mL) draw gives 2 mL of BAC water.
How the Math Works
Every output derives from four identities of dilution arithmetic. Nothing here is peptide-specific — the same math applies to any mass dissolved in any solvent.
- Concentration
- concentration (mcg/mL) = vial mass (mg) × 1,000 ÷ diluent volume (mL)
- Draw volume per dose
- draw (mL) = target amount (mcg) ÷ concentration (mcg/mL)
- Syringe units (U-100)
- units = draw (mL) × 100
- Doses per vial
- doses = vial mass (mcg) ÷ target amount (mcg)
"Target syringe units" mode runs the same identities in reverse, solving the diluent volume that makes one dose land on a chosen syringe marking: diluent (mL) = vial mass (mcg) × target draw (mL) ÷ target amount (mcg).
Worked Example
A 5 mg vial reconstituted with 2 mL of bacteriostatic water yields a concentration of 5,000 mcg ÷ 2 mL = 2,500 mcg/mL. For a target amount of 250 mcg, the draw volume is 250 ÷ 2,500 = 0.1 mL, which is 10 units on a U-100 syringe, and the vial contains 5,000 ÷ 250 = 20 doses.
Open this example pre-filled in the calculator — every calculation produces a shareable link with the values encoded in the URL.
Frequently Asked Questions
How do you calculate peptide concentration after reconstitution?
Concentration is vial mass divided by diluent volume. A 5 mg vial reconstituted with 2 mL of bacteriostatic water gives 2.5 mg/mL, or 2,500 mcg/mL. The arithmetic assumes the labeled mass is entirely peptide; vial contents also include water and counterions, so exact quantitative work applies a net peptide content correction from the batch certificate of analysis.
How much BAC water should I add to a 5 mg vial?
There is no single correct volume. Choose the BAC water volume so the draw for your target aliquot is practical to measure on a U-100 syringe. Two milliliters in a 5 mg vial is a common starting point: 2,500 mcg/mL, so a 250 mcg aliquot is 0.1 mL (10 units). Draws under about 5 units are hard to read; volumes above about 3 mL exceed a standard research vial. Target syringe units mode solves the water volume directly.
How many units is 250 mcg on an insulin syringe?
It depends on concentration, not on the peptide. At 2,500 mcg/mL (5 mg in 2 mL), 250 mcg is 0.1 mL, which is 10 units on a U-100 syringe. At 5,000 mcg/mL (10 mg in 2 mL), the same 250 mcg is 5 units. The calculator converts mL to units with 1 mL = 100 units.
What are units on an insulin syringe?
Standard U-100 insulin syringes are graduated so that 100 units equal 1 mL: one unit is 0.01 mL (10 microliters). A 2,500 mcg/mL solution contains 25 mcg per unit. The calculator converts between mL and units automatically and can display 30-unit, 50-unit, or 100-unit syringes.
Is a BAC water calculator different from a reconstitution calculator?
No. Both are dilution arithmetic. Forward mode (I added the water) takes vial mass and BAC volume and returns concentration and draw. Backward mode (Target syringe units) takes vial mass, target aliquot, and a desired syringe mark and returns how much BAC water to add. This page is both.
Is this calculator medical or dosing advice?
No. It performs concentration arithmetic for laboratory research solutions and nothing else. It does not recommend amounts, routes, or schedules, and it is not guidance for human or veterinary use. All outputs should be verified independently before use in any experimental protocol.
Related Guides
- Peptide Reconstitution, Storage & Stability — solvent selection, technique, and degradation pathways
- Research Peptide Safety — evidence tiers and class-level safety patterns
- How to Evaluate Research Peptide Suppliers — reading COAs and the net peptide content correction
This calculator performs concentration arithmetic for laboratory research solutions. It is provided for educational purposes only, is not medical advice, and is not guidance for human or veterinary use. See the disclaimer for details.