Peptide Reconstitution Calculator
Work out how much bacteriostatic water to add to a vial, what concentration that gives, how many units to draw on an insulin syringe, and what each dose costs. Supports single-peptide dosing, multi-peptide blends, and cost estimates when you enter vial price and schedule.
For research use only. Not medical advice. Always verify calculations and follow sterile technique in laboratory settings.
How reconstitution maths works
A lyophilised vial holds a fixed mass of peptide as dry powder. Adding bacteriostatic water dissolves it into a measurable liquid. Every figure the calculator returns comes from four pieces of arithmetic:
peptide mass (mg) ÷ water added (mL) = mg/mLdose (mg) ÷ concentration (mg/mL) = mLmL × 100 = units on a U-100 syringevial mass (mg) ÷ dose (mg) = dosesDoses are often quoted in micrograms. Divide by 1000 to convert micrograms to milligrams before using these formulas — 250 mcg is 0.25 mg.
A worked example
Reconstituting a 10 mg vial with 2 mL of bacteriostatic water, then drawing a 250 mcg dose:
- 1Concentration
10 mg ÷ 2 mL = 5 mg/mL - 2Dose in mg
250 mcg ÷ 1000 = 0.25 mg - 3Volume to draw
0.25 mg ÷ 5 mg/mL = 0.05 mL - 4Syringe units
0.05 mL × 100 = 5 units - 5Doses per vial
10 mg ÷ 0.25 mg = 40 doses
At 5 units the draw sits near the bottom of the barrel, where each mark is hardest to read. Using 4 mL of water instead halves the concentration and doubles the draw to 10 units — the same 250 mcg, measured more precisely.
Reading the syringe
Insulin syringes are marked in units rather than millilitres. U-100 means 100 units to 1 mL, so one unit is 0.01 mL regardless of barrel size. A larger barrel does not change what a unit means — it changes how much you can draw and how far apart the marks sit.
| Barrel | Holds | Best for |
|---|---|---|
| 0.3 mL | 30 units | Small draws under 30 units, where each mark is easiest to read |
| 0.5 mL | 50 units | Mid-range draws; the usual compromise between range and precision |
| 1.0 mL | 100 units | Larger draws, or dilute preparations needing more volume |
Cost per dose and per milligram
Vial price on its own says nothing useful, because vials differ in size. Dividing price by the milligrams inside gives a figure that compares across vendors, and dividing price by doses per vial gives what a single dose actually costs. The 10 mg vial above at $60 works out at $6.00 per mg and $1.50 per 250 mcg dose.
The vendor comparison lists price per mg across suppliers, and each peptide profile records typical vial sizes and half-life.
Common questions
- Does adding more bacteriostatic water change the dose?
- No. The vial contains a fixed mass of peptide, and adding water does not create or remove any of it. More water lowers the concentration, so the same dose is carried in a larger volume and you draw to a higher mark on the syringe. Less water raises the concentration and the same dose sits at a lower mark. The milligrams delivered are identical either way — only the volume changes.
- How much bacteriostatic water should I add to a peptide vial?
- There is no single correct amount. Choose the volume that puts your intended dose on a syringe mark you can read accurately. A common approach is to pick a round concentration — reconstituting a 10 mg vial with 2 mL gives 5 mg/mL — then check where a typical dose lands. If it falls below about 5 units on a U-100 syringe, add more water so the draw is larger and easier to measure precisely.
- How do I convert a dose in micrograms to insulin syringe units?
- Convert the dose to milligrams by dividing micrograms by 1000, divide that by the concentration in mg/mL to get the volume in mL, then multiply by 100 because a U-100 syringe is graduated at 100 units per mL. For a 250 mcg dose from a 5 mg/mL vial: 250 ÷ 1000 = 0.25 mg, 0.25 ÷ 5 = 0.05 mL, 0.05 × 100 = 5 units.
- How many doses are in a vial?
- Divide the total mass in the vial by the mass of one dose, using the same unit for both. A 10 mg vial dosed at 250 mcg gives 10 ÷ 0.25 = 40 doses. The water volume does not affect this number, because it does not change how much peptide is present.
- How do I work out cost per dose?
- Divide the vial price by the number of doses it contains. A 10 mg vial costing $60 and yielding 40 doses works out at $1.50 per dose. Comparing cost per milligram rather than per vial is the only way to compare vendors whose vials come in different sizes.
- How is a blend of two peptides calculated?
- Both peptides sit in the same vial and share the same water volume, so each has its own concentration derived from its own mass. Once you fix the water volume, the ratio between the two doses is fixed too — a single draw delivers both. Pick the water volume so that the peptide with the tighter dosing requirement lands on a readable mark, then check what the second peptide works out to at that same volume.
- What does mg/mL mean on a reconstituted vial?
- It is the concentration: how many milligrams of peptide are dissolved in each millilitre of liquid. It is the bridge between a dose expressed as a mass and a volume you can actually draw into a syringe. Every other figure on this page derives from it.