Peptide Reconstitution Calculator
Enter your vial size, how much bacteriostatic water you added, and the amount you are measuring. Get the exact insulin syringe units to draw, the resulting concentration, and how many doses the vial holds.
Draw this much
- Volume to draw
- 0.1 mL
- Concentration
- 2.5 mg/mL
- Per 1 unit
- 25 mcg
- Doses per vial
- 20 doses
Common reconstitution chart
Standard vial and water combinations, with the amount contained in a single unit on a U-100 syringe. The last column shows what a 250 mcg measurement works out to at each concentration.
| Vial size | BAC water | Concentration | Per 1 unit | 250 mcg = |
|---|---|---|---|---|
| 2 mg | 1 mL | 2.0 mg/mL | 20 mcg | 12.5 units |
| 2 mg | 2 mL | 1.0 mg/mL | 10 mcg | 25 units |
| 5 mg | 1 mL | 5.0 mg/mL | 50 mcg | 5 units |
| 5 mg | 2 mL | 2.5 mg/mL | 25 mcg | 10 units |
| 5 mg | 3 mL | 1.67 mg/mL | 16.7 mcg | 15 units |
| 10 mg | 1 mL | 10.0 mg/mL | 100 mcg | 2.5 units |
| 10 mg | 2 mL | 5.0 mg/mL | 50 mcg | 5 units |
| 10 mg | 3 mL | 3.33 mg/mL | 33.3 mcg | 7.5 units |
| 10 mg | 5 mL | 2.0 mg/mL | 20 mcg | 12.5 units |
| 15 mg | 3 mL | 5.0 mg/mL | 50 mcg | 5 units |
| 20 mg | 2 mL | 10.0 mg/mL | 100 mcg | 2.5 units |
| 30 mg | 3 mL | 10.0 mg/mL | 100 mcg | 2.5 units |
How the math works
Every reconstitution calculation comes down to three numbers: how much is in the vial, how much liquid you added, and how much you want to measure out. Everything else follows from those.
Step 1 — Find the concentration
Divide the vial amount by the water volume. A 5 mg vial with 2 mL of bacteriostatic water gives 2.5 mg per mL. Adding water never changes how much is in the vial — it only spreads the same amount across more liquid.
Step 2 — Convert to units
A U-100 insulin syringe is marked so that 100 units = 1 mL, which makes one unit exactly 0.01 mL. So 2.5 mg/mL is 2,500 mcg/mL, and dividing by 100 gives 25 mcg in every unit.
Step 3 — Divide your target by that
If you are measuring 250 mcg and each unit holds 25 mcg, you draw to the 10 unit mark. As one formula:
The formula
Units to draw = (target mcg × water mL) ÷ (vial mg × 10)
Worked through with the example above: (250 × 2) ÷ (5 × 10) = 500 ÷ 50 = 10 units.
Why the same amount can be different unit counts
This trips people up constantly. Units measure volume, not amount. The same 250 mcg is 10 units in a vial mixed with 2 mL, but only 5 units if that same vial was mixed with 1 mL. A unit count is meaningless unless you know the concentration it came from — which is exactly why it is worth recording the mixing volume alongside every vial.
Choosing how much water to add
There is no universally correct volume, and the calculator does not try to pick one for you. The tradeoff is readability against capacity:
- More water spreads the same amount over a larger volume, so each measurement lands on a bigger, easier-to-read part of the syringe. Small amounts become far less error-prone.
- Less water means very small draws — sometimes 2 or 3 units — where a slight misread is a large proportional difference.
- Too much water can push a single draw past the capacity of the syringe barrel, or past the volume the vial can physically hold.
The calculator flags both problems: it warns when a draw falls below roughly 5 units, where precision suffers, and when it exceeds the syringe you selected.
Frequently asked questions
How do you calculate peptide reconstitution?
Divide the vial amount by the water volume to get concentration, then convert to units knowing that one unit on a U-100 syringe is 0.01 mL. The combined formula is: units = (target mcg × water mL) ÷ (vial mg × 10).
How much bacteriostatic water should I add to a vial?
There is no single correct volume, and this is a question for the documentation supplied with your product and your healthcare provider. Mechanically, the volume only changes the concentration — more water makes each draw larger and easier to measure accurately, less water makes it smaller.
How many units is 250 mcg on an insulin syringe?
It depends entirely on concentration. With a 5 mg vial in 2 mL, 250 mcg is 10 units. With the same vial in 1 mL, it is 5 units. Always calculate against the concentration you actually mixed.
What does a unit mean on an insulin syringe?
On a standard U-100 syringe, 100 units equals 1 mL, so one unit is 0.01 mL. This holds whether the barrel is 0.3 mL (30 units), 0.5 mL (50 units), or 1 mL (100 units) — only the maximum capacity differs.
Does the calculator work for mg doses and IU?
Yes. Switch the unit selector next to the amount field. Milligrams and micrograms convert directly. IU is not a fixed mass — the conversion depends on the compound — so the tool asks you to supply the IU-per-mg ratio from your own product documentation rather than assuming one.
Does this calculator recommend a dose?
No. It performs arithmetic on numbers you enter and nothing else. It does not suggest compounds, amounts, or schedules, and it has no way to verify vial contents. See the PepTrack guides for organizational guidance, or a qualified healthcare professional for anything medical.
Stop recalculating every time
PepTrack keeps the mixing volume, concentration, and unit count saved with each vial — so you calculate once, then just log. Free on iPhone, no account required.
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