Peptide Reconstitution Calculator

10mg vial, 2ml of water, 250mcg per draw

• Concentration: (10 × 1000) ÷ 2 = 5,000 mcg/ml, which is 5 mg/ml.
• Draw volume: 250 ÷ 5,000 = 0.05 ml.
• Syringe reading: 0.05 × 100 = 5 units on a U-100 barrel.
• Draws per vial: (10 × 1000) ÷ 250 = 40.

10mg vial, 250mcg per draw, landing on 10 units (reverse mode)

• Water: (10 × 10 × 10) ÷ 250 = 4 ml.
• Check: 10mg in 4ml is 2,500 mcg/ml, so 250mcg is 0.1ml — 10 units.
• The vial still holds 40 draws; only the dilution changed, not the amount per draw.

The same draw on a U-40 barrel instead of U-100

• 10mg in 2ml is 5,000 mcg/ml, so 250mcg is 0.05ml — the volume is a physical fact and does not change.
• U-100 reading: 0.05 × 100 = 5 units.
• U-40 reading: 0.05 × 40 = 2 units.
• Same syringe volume, two different numbers. Reading a U-40 barrel as though it were U-100 is the most common measurement error in reconstitution work.

5mg vial, 1ml of water, 500mcg per draw

• Concentration: (5 × 1000) ÷ 1 = 5,000 mcg/ml.
• Draw volume: 500 ÷ 5,000 = 0.1 ml, which is 10 units.
• Draws per vial: (5 × 1000) ÷ 500 = 10.

How much bacteriostatic water do I add to a peptide vial?

There is no single correct volume — the water only sets the concentration, not the amount of peptide, which is fixed by the vial. More water gives a weaker solution and a larger, easier-to-read draw; less water gives a stronger solution and a smaller draw. Most researchers pick the volume that puts their intended draw on a clean syringe graduation, which is what the reverse mode of this calculator solves for. In practice most preparations land between 1ml and 5ml, not because that range is recommended but because it is the one that keeps the draw on a readable part of the barrel for common vial sizes — which is what the table above computes for your own figures.

How many units is 250mcg?

It depends entirely on the concentration, so the question cannot be answered without the vial size and the water volume. In a 10mg vial reconstituted with 2ml the solution is 5,000 mcg/ml, so 250mcg is 0.05ml — 5 units on a U-100 insulin syringe. The same 250mcg from the same 10mg vial reconstituted with 4ml is 0.1ml, or 10 units. Enter your own numbers above to convert.

What does U-100 mean on an insulin syringe?

U-100 describes the graduation scale: the barrel is marked so that 100 units equals 1 millilitre. That ratio is the same on 0.3ml, 0.5ml and 1ml barrels — only the total capacity and the spacing of the printed marks change. So one unit is always 0.01ml, and a volume in millilitres becomes units by multiplying by 100.

What syringe do I need for a reconstituted research peptide?

For small volumes, a U-100 insulin syringe: a 0.3ml barrel holds 30 units and has the widest-spaced graduations, a 0.5ml barrel holds 50 units, and a 1ml barrel holds 100 units but is usually printed in 2-unit steps. Pick the smallest barrel that comfortably holds the draw — the graduations are further apart, so the reading is more precise. Larger transfers are handled with a standard graduated laboratory syringe.

How long does a reconstituted peptide last?

Peptides in solution are markedly less stable than the lyophilised powder, because in water they are exposed to hydrolysis, oxidation and aggregation. Stability in solution is compound-specific and batch-specific rather than a single number, which is why solutions are generally prepared according to the experimental protocol and stored refrigerated, protected from light. The batch record is the reference for any specific material — see our storage and handling guide.

Does the concentration change if I use a bigger vial?

Yes. Concentration is peptide divided by water, so a 10mg vial in 2ml is twice the concentration of a 5mg vial in 2ml, and the draw volume for the same amount halves. That is why the vial strength and the water volume must both be entered — one on its own tells you nothing about what a given draw contains.

Why does my draw land between the syringe marks?

Because the concentration you have produced does not divide neatly into the barrel's graduations. Nothing is wrong with the solution — it is a measurement problem, and it is fixed by changing the dilution rather than by estimating between marks. Enter the unit reading you want in reverse mode and the calculator returns the water volume that produces it.

Can I add more water later to a vial I already reconstituted?

Adding diluent to an already-reconstituted vial changes the concentration of everything in it, so every previously calculated draw volume becomes wrong and has to be recalculated from the new total volume. It also adds another handling step to a solution that is already less stable than the powder. Working out the volume before the first reconstitution avoids both problems.

What is bacteriostatic water and why is it used?

Bacteriostatic water is sterile water containing 0.9% benzyl alcohol, a preservative that inhibits bacterial growth so a vial can be entered more than once. That is why it is the standard diluent for reconstitution work rather than plain sterile water. We supply it in 3ml and 10ml formats as a laboratory reagent.

What is the difference between a U-100 and a U-40 syringe?

The number is the graduation scale: a U-100 barrel is marked so 100 units equals 1ml, a U-40 barrel so 40 units equals 1ml. The same physical 0.05ml draw therefore reads 5 units on U-100 and 2 units on U-40 — a 2.5-fold difference in the number, with no difference in what is in the barrel. U-100 is the common format in the UK, but U-40 barrels are still sold, so the scale printed on the barrel is worth checking before measuring rather than after.

How do I convert mg/ml into a molar concentration?

Divide the concentration in milligrams per millilitre by the compound's molecular weight in grams per mole, because mg/ml and g/L are the same quantity. BPC-157 has a molecular weight of 1419.6 g/mol, so a 5 mg/ml solution is 5 ÷ 1419.6 = 0.00352 mol/L, or 3.52 mM. Selecting a compound from the presets above does this automatically from the molecular weight published on its compound page.

How much of each peptide is in a draw from a blend vial?

A blend label states an arithmetic total of separately weighed peptides, so a draw delivers each component in the ratio it was weighed at, not the label figure. Our 70mg blend is 10mg BPC-157, 50mg GHK-Cu and 10mg TB-500, so a 700mcg draw contains 100mcg, 500mcg and 100mcg respectively. Selecting a blend from the presets splits the draw automatically. Equal masses are also not equal molar amounts, because the components have different molecular weights.

Can I set the amount by dragging the syringe?

Yes — the barrel on this page is an input, not an illustration. Drag the plunger and the amount per draw follows it; type an amount and the plunger moves to match. Dragging snaps to the graduations printed on the barrel you have selected, so the draw always lands on a mark you could actually read rather than between two of them. The arrow keys move it one graduation at a time, Home empties the barrel and End fills it, and the whole control is exposed to screen readers as a slider reporting the current reading in units and millilitres.

Why does the calculator show several water volumes at once?

Because choosing a water volume is a trade-off rather than a calculation with one right answer, and the usual way to resolve it is trial and error. The table shows what every common volume does to the syringe reading for the amount you entered, and flags the ones landing on a printed graduation, so the trade-off is visible in one look. The amount per draw is identical in every row — only the dilution, and therefore the reading, changes.

Does this calculator tell me how much to use?

No. It performs arithmetic on the numbers you enter and nothing else. It has no default amount, suggests no amount, and holds no protocols, schedules or titration logic. Everything Index Peptides supplies is a research material for in-vitro laboratory use only, and the experimental design is the qualified researcher's responsibility.