Pick your peptide below for a calculator preloaded with its vial sizes and documented protocols, or use the general calculator to enter any values by hand.
Pick a compound for a calculator preloaded with its common vial sizes and documented protocols — it returns the exact units to draw and how many doses a vial yields.
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Research-context arithmetic only. The steps below convert vial strength, water volume and dose into concentration and syringe units — they explain the math, not a dosing recommendation. Figures in the worked example are illustrative. Consult a licensed physician for personal medical decisions.
Reconstitution math is two divisions. Everything the calculator above does reduces to these two steps, and knowing them makes it obvious when a result looks wrong.
Step 1 — concentration
peptide (mg) ÷ water (mL) = concentration (mg/mL)
Step 2 — volume to draw
dose ÷ concentration = volume (mL) → × 100 = units on a U-100 syringe
The one conversion that trips people up sits between those steps: doses are usually quoted in micrograms while vials are labelled in milligrams. There are 1,000 mcg in 1 mg, and mixing the two up moves a result by a factor of a thousand — the single most common arithmetic error in reconstitution.
Take a 10 mg vial, 2 mL of bacteriostatic water, and a 250 mcg dose. The numbers are arbitrary — this is the arithmetic, not a protocol.
Using 1 mL of water instead of 2 mL makes the same dose 2.5 units; 5 mL makes it 12.5 units. The vial still holds 40 doses in every case. Water volume changes how the dose is measured, never how much peptide is present.
On a U-100 insulin syringe, 1 mL is 100 units, so a single unit is 0.01 mL. Syringe capacity and that scale are separate things — a 0.3 mL syringe is still graduated in U-100 units, it simply stops at 30 of them.
| Syringe | Holds | Practical note |
|---|---|---|
| 0.3 mL | 30 units | Finest graduations; smallest volume per draw. |
| 0.5 mL | 50 units | Middle ground — the most common insulin syringe. |
| 1.0 mL | 100 units | Holds a full millilitre; graduations are coarsest. |
Common vial-and-water combinations, with what one syringe unit works out to in each. Reading across shows how coarse or fine the resulting measurement is.
| Vial | Water | Concentration | 1 unit = |
|---|---|---|---|
| 5 mg | 1 mL | 5 mg/mL | 50 mcg |
| 5 mg | 2 mL | 2.5 mg/mL | 25 mcg |
| 10 mg | 1 mL | 10 mg/mL | 100 mcg |
| 10 mg | 2 mL | 5 mg/mL | 50 mcg |
| 10 mg | 5 mL | 2 mg/mL | 20 mcg |
| 15 mg | 3 mL | 5 mg/mL | 50 mcg |
| 20 mg | 2 mL | 10 mg/mL | 100 mcg |
| 20 mg | 4 mL | 5 mg/mL | 50 mcg |
The math above is identical for every compound; what differs is vial sizing, documented protocol ranges and storage. The calculators by peptide at the top of this page come preloaded with each compound's vial sizes, and every peptide's reconstitution guide covers its handling and mixing chart in full.
Two steps. First divide the peptide mass by the water volume to get concentration: a 10 mg vial plus 2 mL of bacteriostatic water is 5 mg/mL, or 5,000 mcg/mL. Then divide the dose by that concentration to get volume: 250 mcg divided by 5,000 mcg/mL is 0.05 mL. On a U-100 syringe that volume is read as 5 units (× 100).
There is no single correct volume. The water only sets concentration — the amount of peptide in the vial does not change. Larger volumes make each dose easier to measure accurately; smaller volumes concentrate it. A common approach is choosing the volume that lands a typical dose on a round number of syringe units, because a whole-number draw is harder to misread.
On a U-100 insulin syringe, 1 mL equals 100 units, so one unit is 0.01 mL. This is the conversion most reconstitution math depends on. A U-50 syringe is graduated differently, and a 0.3 mL syringe holds 30 units rather than 100 — the unit marks are a volume scale, not a dose scale.
The arithmetic is the same for any vial size: pick a water volume, then divide. 10 mg with 1 mL gives 10 mg/mL; with 2 mL, 5 mg/mL; with 5 mL, 2 mg/mL. Each of those makes a given dose a different number of units to draw, which is the only practical difference between them.
Sterile water contains no preservative. Bacteriostatic water contains benzyl alcohol, which is what allows a reconstituted vial to be stored and drawn from more than once. Without it, compounding-pharmacy and manufacturer handling guidance commonly treats the solution as single-use.
Only negligibly at these quantities. A few milligrams of lyophilised powder displaces a volume too small to matter against 1-5 mL of water, so the standard calculation treats the final volume as the water volume added.
This calculator and the notes above cover dilution arithmetic only. Figures used in the examples are illustrative, not dosing recommendations. Peptides discussed across this site are research compounds; consult a licensed physician for personal medical decisions.