Reconstituting a research peptide comes down to one question: once the bacteriostatic water is in the vial, how much do you actually draw? This calculator does that arithmetic for every compound in our catalogue. Pick a peptide, enter how much water you added and the dose you’re targeting, and it returns the exact number of units on an insulin syringe.

How to use it

1. Choose your compound. The vial strength fills in automatically from our catalogue — Retatrutide 10mg, GHK-Cu 100mg, NAD+ 500mg and so on. Pick "Custom" for anything else.
2. Enter the bacteriostatic water you added. Most 10mg vials are reconstituted with 1–3 mL. More water means a weaker solution and a larger, easier-to-measure draw.
3. Set your target dose. Switch between mcg and mg (HCG switches to IU automatically, since it is measured differently).
4. Read the units. That is the mark to draw to on a U-100 insulin syringe.

The math behind it

Reconstitution is a two-step conversion. First you find the concentration:

Concentration (mg/mL) = vial strength (mg) ÷ water added (mL)

A 10mg vial with 2 mL of bacteriostatic water gives 5 mg/mL. Then you convert your dose to a volume, and the volume to syringe units:

Volume (mL) = dose (mg) ÷ concentration (mg/mL)
Units = volume (mL) × 100  (on a U-100 syringe, 1 mL = 100 units)

So a 250 mcg dose from that 5 mg/mL vial is 0.05 mL, or 5 units. The calculator handles the decimal places so you are not doing this by hand.

Choosing how much water to add

There is no single correct volume — it is a trade-off. Less water gives a concentrated solution and a very small draw, which is harder to measure precisely. More water gives a bigger, more accurate draw but uses more syringe capacity. As a rule of thumb, aim for a draw somewhere between 10 and 50 units: precise enough to measure, small enough to fit. The calculator flags both failure modes, warning you if a draw falls under 2 units or exceeds what the syringe holds.

Common questions

How many units is 250 mcg?

It depends entirely on concentration. From a 10mg vial with 2 mL water (5 mg/mL), 250 mcg is 5 units. From the same vial with 1 mL water (10 mg/mL), it is 2.5 units. The vial strength alone never tells you the answer — you need the water volume too.

What syringe should I use?

U-100 insulin syringes are standard for this work. The calculator supports 1 mL, 0.5 mL and 0.3 mL barrels; the tick marks on the diagram redraw to match whichever you select.

How long does a reconstituted vial last?

Once mixed, solutions are generally kept refrigerated at about 4 °C and used within roughly 28 days. Sealed lyophilized powder is stored colder and lasts far longer. See our reconstitution and storage guide for the detail.

Why does HCG use IU instead of mcg?

HCG is measured in international units, a measure of biological activity rather than mass, so it cannot be converted to milligrams. Select HCG and the dose field switches to IU automatically.

This calculator performs unit-conversion arithmetic for laboratory research only. It is not medical, dosing, or veterinary guidance. The compounds referenced are supplied as research chemicals and are not approved health products in Canada.