Free Tool
Peptide Reconstitution Calculator
Enter what is in the vial, how much bacteriostatic water you added, and the dose you are measuring. The calculator returns the concentration, the exact volume to draw, and the reading on a standard U-100 insulin syringe.
Draw to this mark
—
Reading on the syringe barrel
- Volume per dose
- —
- The physical liquid you are drawing.
- Concentration
- —
- How much peptide sits in each millilitre.
- Per syringe unit
- —
- Peptide contained in one 0.01 mL tick.
- Doses per vial
- —
- Full doses the reconstituted vial holds.
This tool converts units of mass and volume. It does not recommend a dose, a compound, or a schedule. Peptides sold through the vendors listed on this site are supplied for laboratory research use only.
The math
What Makes It Authentically Accurate?
Nothing here is estimated or modelled. Every number on this page comes from two fixed conversions and one property of liquids, so the arithmetic holds for any compound you put in the vial.
Standardized fluid metrics
The calculator works in units of measure that are defined the same way everywhere, not approximated:
- 1 milligram (mg) = 1,000 micrograms (mcg)
- 1 millilitre (mL) = 100 units on a standard U-100 syringe
- 1 unit = 0.01 mL
Fixed physics
One millilitre of fluid occupies exactly the same volume regardless of which compound is dissolved in it. A 5 mg peptide and a 15 mg peptide dissolved in 2 mL both give you 2 mL of solution — only the concentration changes. That is why the syringe reading can be derived from volume alone, and why, as long as the numbers you enter are correct, the output math cannot fail.
How each value is calculated
Convert the vial to micrograms
total mcg = vial mg × 1,000
Doses are usually spoken about in micrograms while vials are labelled in milligrams. Everything is converted to micrograms first so the two never get mixed up.
Work out the concentration
concentration (mcg/mL) = total mcg ÷ water added (mL)
This is the only step where the bacteriostatic water matters. Adding more water does not change how much peptide is in the vial — it spreads the same mass across more liquid, which lowers the concentration and makes each dose a larger, easier-to-read volume.
Turn the dose into a volume
volume (mL) = dose (mcg) ÷ concentration (mcg/mL)
Dividing the mass you want by the mass sitting in each millilitre gives the millilitres you need to draw. The micrograms cancel out and volume is what remains.
Convert the volume to syringe units
units = volume (mL) × 100
A U-100 syringe is graduated so that its full millilitre is split into 100 ticks. Multiplying millilitres by 100 gives the mark to fill to — this is the number you actually read off the barrel.
Count the doses in the vial
doses per vial = total mcg ÷ dose (mcg)
Independent of water and syringe size. The solvent changes how much liquid each dose takes up, never how many doses the vial contains.
Worked example
A 10 mg vial reconstituted with 2 mL of bacteriostatic water, measuring a 500 mcg dose:
- Total peptide10 mg × 1,00010,000 mcg
- Concentration10,000 mcg ÷ 2 mL5,000 mcg/mL
- Volume per dose500 mcg ÷ 5,000 mcg/mL0.1 mL
- Syringe reading0.1 mL × 10010 units
- Doses per vial10,000 mcg ÷ 500 mcg20
Draw to the 10-unit mark on a U-100 syringe. Reconstitute the same vial with 1 mL instead and the concentration doubles to 10,000 mcg/mL, so the same 500 mcg dose becomes 0.05 mL — 5 units. The dose is identical; only the volume carrying it changed.
Volume to syringe units at a glance
| Volume | U-100 units | Fraction of 1 mL |
|---|---|---|
| 0.05 mL | 5 units | 1/20 |
| 0.10 mL | 10 units | 1/10 |
| 0.20 mL | 20 units | 1/5 |
| 0.25 mL | 25 units | 1/4 |
| 0.50 mL | 50 units | 1/2 |
| 1.00 mL | 100 units | 1 |
Valid for any U-100 syringe, whatever its capacity — the graduations are the same, there are simply fewer of them on a smaller barrel.
FAQ
Questions About the Calculator
How the inputs behave and what the results mean.
- No. The water changes the concentration and therefore the volume you draw, never the amount of peptide in that volume. A 5 mg vial holds 5 mg whether you add 1 mL or 3 mL. More water simply spreads the same mass over more liquid, which puts each dose further along the syringe barrel and makes it easier to read accurately.
- Vials are labelled in milligrams while doses are usually described in micrograms, and mixing the two is the most common source of error by a factor of 1,000. Converting everything to micrograms first (1 mg = 1,000 mcg) removes that risk. You can enter either unit — the conversion happens internally.
- U-100 describes the graduation scale, not the size of the barrel: 100 units per millilitre, so one unit is 0.01 mL. A 1 mL, 0.5 mL, and 0.3 mL syringe all use that same scale and simply carry 100, 50, and 30 marks respectively. Because the ticks are identical, the unit reading the calculator gives is the same on all three.
- The volume you need exceeds the barrel's capacity, so you would have to draw more than once. Reconstituting with less bacteriostatic water raises the concentration and shrinks the volume per dose — change the water figure and the calculator will show the new reading immediately.
- Anything below roughly 5 units is hard to measure precisely on a U-100 barrel, since you are working inside a few graduations. Adding more bacteriostatic water is the usual fix: it lowers the concentration, so the same dose spans more ticks and rounding error stops mattering as much.
- The lyophilised powder is a very small mass and the volume it contributes once dissolved is negligible at these quantities — well below what a syringe can resolve. Standard practice is to treat the volume of solution as the volume of solvent added, which is what this calculator does.
Sourcing your next vial?
Compare vetted suppliers, check their third-party lab reports, and pick up a verified discount code before you order. Find the code that saves the most on your cart, see how we vet suppliers or read the research blog for background.