What this calculator does
A peptide calculator, in the sense most people searching for one mean, is a mixing and dosing-volume tool: it takes the amount of peptide powder in a vial, the amount of liquid used to dissolve it, and a target dose, and works out how much liquid to draw up in a syringe to deliver that dose. It is arithmetic, not chemistry advice, but getting that arithmetic right matters because a small mixing error changes every dose drawn from the same vial.
The maths is the same C1V1-style dilution used anywhere a dry substance is dissolved into a liquid to a target strength, but this calculator is built around the units and syringe markings peptide users actually work with: milligrams in the vial, millilitres of liquid added, micrograms per dose, and insulin-syringe units on the draw.
The formula
The peptide amount is converted to micrograms and divided by the liquid volume added to get the concentration in micrograms per millilitre. The target dose is then divided by that concentration to get the volume to draw for one injection, which is also converted to units on a standard U-100 insulin syringe, where 100 units equals 1 millilitre.
| Term | Meaning |
|---|---|
| Concentration | How much peptide is in each millilitre of liquid after mixing: vial amount (mcg) ÷ liquid added (mL). |
| Dose volume | The amount of liquid to draw up for one dose: target dose (mcg) ÷ concentration (mcg/mL). |
| U-100 syringe units | The scale printed on a standard insulin syringe, where the full 1 mL barrel is marked as 100 units, so 1 unit = 0.01 mL. |
The inputs explained
| Field | What to enter |
|---|---|
| Peptide amount in vial (mg) | The total amount of peptide in the vial, as stated on the label. |
| Liquid added (e.g. bacteriostatic water) (mL) | The volume of liquid (commonly bacteriostatic water) used to dissolve the powder. |
| Target dose per injection (mcg) | The amount you intend to draw up and use in a single injection. |
When to use it
Working out the draw volume for a vial you have just mixed
Once a vial is reconstituted, the concentration is fixed for its whole life; entering the vial size and liquid added once, then trying different target doses, shows the exact volume to draw for each without re-doing the arithmetic by hand every time.
Choosing how much liquid to add in the first place
A smaller liquid volume gives a stronger, more concentrated mix and a smaller draw volume per dose, which can be harder to measure precisely on a low-resolution syringe; a larger liquid volume gives a weaker mix and an easier-to-read draw volume, at the cost of needing more liquid on hand.
Checking how many doses a vial will actually provide
Dividing the total peptide amount by the intended per-dose amount gives the number of full doses in the vial, which is useful for working out how long a vial should last before it needs replacing.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How the draw volume changes with a larger target dose, at a fixed mix
The same reconstituted vial, drawn up to a range of target doses.
| Target dose | Volume to draw for this dose | On a U-100 insulin syringe | Doses available in this vial |
|---|---|---|---|
| 50 mcg | 0.020 mL | 2.0 units | 100.0 |
| 100 mcg | 0.040 mL | 4.0 units | 50.0 |
| 150 mcg | 0.060 mL | 6.0 units | 33.3 |
| 250 mcg | 0.100 mL | 10.0 units | 20.0 |
| 500 mcg | 0.200 mL | 20.0 units | 10.0 |
| 1000 mcg | 0.400 mL | 40.0 units | 5.0 |
How the mixing concentration changes with the amount of liquid added
The same vial, mixed with a range of liquid volumes.
| Liquid added | Concentration after mixing | Volume to draw for this dose | On a U-100 insulin syringe |
|---|---|---|---|
| 1 mL | 5,000 mcg/mL (5.000 mg/mL) | 0.050 mL | 5.0 units |
| 1.5 mL | 3,333 mcg/mL (3.333 mg/mL) | 0.075 mL | 7.5 units |
| 2 mL | 2,500 mcg/mL (2.500 mg/mL) | 0.100 mL | 10.0 units |
| 2.5 mL | 2,000 mcg/mL (2.000 mg/mL) | 0.125 mL | 12.5 units |
| 3 mL | 1,667 mcg/mL (1.667 mg/mL) | 0.150 mL | 15.0 units |
| 5 mL | 1,000 mcg/mL (1.000 mg/mL) | 0.250 mL | 25.0 units |
Questions
What liquid should I use to reconstitute a peptide?
This calculator only handles the volume and concentration arithmetic, not sourcing or handling. Bacteriostatic water is commonly used because it resists bacterial growth over repeated draws, but what to use, and whether to use a peptide at all, is a question for a qualified prescriber, not a calculator.
Why does the draw volume come out so small?
A concentrated mix, from a small liquid volume relative to the peptide amount, produces a small draw volume per dose. That is normal, but it also means small measuring errors have a bigger relative effect, which is one reason people mix with more liquid when precision on a standard syringe matters.
What is a U-100 insulin syringe unit?
It is the marking scale on a standard insulin syringe, where the full barrel holds 100 units in 1 mL. A dose in millilitres can be read off the same syringe as units by multiplying the millilitre figure by 100.
Is this medical or dosing advice?
No. It converts a vial size, a liquid volume and a target dose into a concentration and a draw volume, nothing more. Any decision about what to use, at what dose, and whether it is appropriate at all, belongs with a qualified prescriber.
For the same style of dilution arithmetic applied to a general dried sample rather than a peptide dose, see the resuspension calculator. For diluting a liquid down to a weaker concentration, see the dilution calculator.