Peptide Reconstitution Calculator
For laboratory research use only. Not for human or veterinary use. This tool performs arithmetic on numbers you enter. It is not guidance on what to prepare or why.
Reconstitution arithmetic is simple, and it is still the step most often got wrong — usually because it is done in a hurry, on a phone, next to an open vial. Enter the three numbers below and the concentration, the draw volume and the number of draws fall out of them.
A standard U-100 insulin syringe is marked 0–100 units across 1 ml, so 1 unit is 0.01 ml. That is the conversion used above. Check the barrel: U-40 and 0.5 ml syringes are marked differently and the unit figure will not transfer.
Switching the vial to IU switches the draw to IU with it. It does not convert between the two: how many International Units a milligram comes to depends on the substance, and for some there is no mass equivalent at all. Use whichever unit is printed on your vial, for both boxes.
The arithmetic, written out#
Nothing here is hidden. Three lines of maths:
| What | How |
|---|---|
| Concentration | amount in the vial ÷ solvent (ml) = per ml |
| In micrograms | mg/ml × 1000 = mcg/ml (milligram vials only) |
| Volume per draw | amount wanted ÷ concentration = ml |
| Insulin-syringe units | ml × 100 = units on a U-100 barrel |
A 10mg vial reconstituted with 2ml of solvent gives 5mg/ml, which is 5000mcg/ml. A 250mcg draw from that is 0.05ml, or 5 units on a U-100 syringe, and the vial holds 40 such draws.
The same arithmetic runs on a vial labelled in International Units, which is how a few are sold — the figure on the label is an activity, not a mass, and the sums do not care which. A 5,000 IU vial in 2ml gives 2,500 IU/ml; a 500 IU draw from that is 0.2ml, or 20 units on a U-100 barrel, and the vial holds 10 such draws. Switch the box above to IU and both figures stay in IU.
What this will not do is convert between the two, and that is deliberate rather than missing. How many International Units a milligram comes to is a property of the substance, not a constant: it is roughly 3 IU per mg for somatropin, and for a glycoprotein assayed by activity there is no meaningful mass equivalent at all. A box that turned one into the other would be wrong for most of what is in our catalogue, and wrong in the way that looks authoritative. Use the unit printed on your own vial, in both boxes.
What changes the answer, and what does not#
Solvent volume does not change how much peptide you have. A 10mg vial contains 10mg whether you add 1ml or 5ml. More solvent makes a weaker solution and a larger draw volume; less makes a stronger one and a smaller draw. The total is fixed at the point of manufacture.
That matters because very small draw volumes are hard to measure accurately. A draw of 2 units on a 100-unit barrel is two marks wide, and the error on that is proportionally large. If the arithmetic above gives you a volume you cannot read confidently off the syringe, the answer is usually more solvent, not a steadier hand.
Dead volume is real and it is not in this calculation. Every syringe retains a small amount in the hub and needle that never leaves. On a 30G insulin syringe with a fixed needle that is around 0.5 µl; on a syringe with a detachable needle it can be fifty times that. Across a vial's worth of draws it adds up, which is why the number of draws above is a ceiling rather than a promise. More on syringe choice.
The label is a starting assumption, not a measurement. This calculator trusts the number you type for vial content. Whether the vial actually holds what the label says is a question for the certificate of analysis, not for arithmetic — and the two are often confused. How much is actually in the vial.
Common combinations#
The same figures, worked out in advance. Concentrations in mcg/ml, with the U-100 units for a 250mcg draw in brackets.
| Vial | +1 ml | +2 ml | +3 ml | +5 ml |
|---|---|---|---|---|
| 2 mg | 2000 (12.5u) | 1000 (25u) | 667 (37.5u) | 400 (62.5u) |
| 5 mg | 5000 (5u) | 2500 (10u) | 1667 (15u) | 1000 (25u) |
| 10 mg | 10000 (2.5u) | 5000 (5u) | 3333 (7.5u) | 2000 (12.5u) |
| 20 mg | 20000 (1.25u) | 10000 (2.5u) | 6667 (3.75u) | 4000 (6.25u) |
Read along the 10mg row and the point about measurability makes itself: at 1ml a 250mcg draw is two and a half units, which is a fiddly thing to read. At 3ml it is seven and a half, which is not.
Before any of this applies#
The arithmetic is the easy half. The handling is where material is lost: letting the vial reach room temperature, running the solvent down the glass wall rather than onto the powder, and never shaking. The full reconstitution procedure covers all of it, and the troubleshooting guide covers what a cloudy or foaming vial is telling you.
On solvent: bacteriostatic water contains 0.9% benzyl alcohol and tolerates repeated entry over weeks; sterile water has no preservative and is a single-use proposition. If the calculator says your vial holds forty draws, the solvent choice is what decides whether forty draws is realistic.
Pioneer Research Peptides — UK supplier of research peptides for laboratory use. Ask about batch documentation before you order.
For laboratory research use only — not for human consumption. 18+.
The consumables this assumes#
BAC Water for repeat draws, Sterile Water for single use, and 1ml 30G insulin syringes with the lowest dead volume.