Tools / Reconstitution
Peptide reconstitution calculator
Enter what's in your vial, how much water you mixed in and your dose. You'll see which line to fill your insulin syringe to.
Example: 5 mg vial + 2 mL water = 2.5 mg/mL. A 250 mcg dose is 0.1 mL, the 10-unit line.
The mg printed on the vial label.
Bacteriostatic (bac) water, in mL.
Check whether it says mcg or mg. They differ by 1,000 times.
It's printed on the packet: 0.3, 0.5 or 1 mL.
5 mg vial + 2 mL water → 250 mcg dose
Fill your syringe to
10units
The 10 line on a 1 mL syringe, which is 0.1 mL.
- Strength after mixing
- 2.5 mg/mL
- Each unit holds
- 25 mcg
- Doses in this vial
- 20
Show the math
- 5 mg × 1,000 = 5,000 mcg in the vial
- 5,000 mcg ÷ 2 mL = 2,500 mcg/mL
- 250 mcg ÷ 2,500 mcg/mL = 0.1 mL
- 0.1 mL × 100 units/mL = 10 units
Not what you expected? Check the numbers above, and confirm with your prescriber or pharmacist before you inject.
Checked 8 November 2026 by the PeptideTracker editorial team · This tool does the math only. It doesn't recommend a dose.
[02] Units table
Units to draw from a 5 mg vial
Each number is the line to fill to on a 1 mL (100-unit) insulin syringe. The highlighted one matches the example above.
| Dose | 1 mL water | 2 mL water | 3 mL water |
|---|---|---|---|
| 100 mcg | 2 | 4 | 6 |
| 250 mcg | 5 | 10 | 15 |
| 500 mcg | 10 | 20 | 30 |
| 1,000 mcg | 20 | 40 | 60 |
[03] How to use it
Three numbers, one answer
- Your vial. The amount printed on the label, in mg. Tap a common size or type your own.
- The water. How much bacteriostatic (bac) water you mixed in, in mL.
- Your dose. Check whether it's written in mcg or mg. They differ by 1,000 times, and the calculator tells you if a number looks like the wrong one.
The answer is the line to fill your syringe to. If it falls between two lines, you'll see the nearest line and how close it is.
[04] Questions
Questions
How many units is 250 mcg?
With 5 mg of peptide mixed into 2 mL of water, each unit on a U-100 syringe holds 25 mcg, so 250 mcg is 10 units. With 3 mL of water it is 15 units.
How much bacteriostatic water should I add?
There is no single correct amount. More water spreads each dose over more units, which makes small doses easier to measure. Less water means a smaller volume per injection. Pick an amount where your dose fits the syringe and lands on one of its marks.
What is a unit on an insulin syringe?
On a U-100 insulin syringe, 100 units equals 1 mL, so 1 unit is 0.01 mL. Units measure volume, not the amount of peptide. The amount of peptide in each unit depends on how the vial was mixed.
Does this work for tirzepatide, semaglutide and other GLP-1 vials?
Yes. The math is the same for any powder or compounded vial: total mg in the vial, divided by the mL of liquid, gives the strength. For pre-filled pens, follow the dose steps on the pen's label instead.
Spotted a mistake or something out of date? Tell us. We aim to fix factual errors within two working days.
[05] Read next
Guides that go with this calculator
- How to reconstitute peptidesMixing (reconstituting) means adding bacteriostatic (bac) water to the freeze-dried powder in your vial so you can measure out doses. How much water you add, and how you add it, sets every dose that follows.
- How much bac water to add to a peptide vialThere's no single right amount. The water sets how much peptide each unit on your syringe holds, so choose an amount that puts your dose on a line you can read.
- Tirzepatide dosage chart: mg, mL and unitsPrescriptions say mg and syringes say units. This chart lines up each Mounjaro and Zepbound label dose with its mL and U-100 units.
- Semaglutide dosage chart: mg, mL and unitsPens give you a set dose in mg. If your semaglutide comes from a vial, each label dose also has to become mL and syringe units.
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