Peptide Calculator
Enter your vial and dose to get the exact amount to draw — down to the insulin unit.
🧑⚕️ New to mixing, or prescribed a dose? Try the step-by-step guide →Enter your vial amount, water, and dose to see exactly how many units to draw.
How to use the peptide calculator
This peptide reconstitution calculator turns the one relationship people get stuck on — vial size, bacteriostatic water, and dose — into a single number: exactly how many units to draw on an insulin syringe. You don’t need to remember any formulas. Enter three things and read the result:
- Peptide in the vial (mg). The total milligrams of peptide in your vial, from the label — e.g. 5 mg or 10 mg.
- Bacteriostatic water (mL). How much water you’re adding to reconstitute it. This is your choice — it changes how many units you draw, not the dose itself. 1–3 mL is typical.
- Target dose. The amount you want per injection, in micrograms (mcg) or milligrams (mg).
- Read the units to draw. The calculator shows the exact fill line on a U-100 insulin syringe, plus your concentration, how many doses the vial holds, and a plain-English summary.
A worked example
Say you have a 5 mg vial and add 2 mL of bacteriostatic water, and you want a 250 mcg dose:
- 5 mg × 1,000 = 5,000 mcg of peptide in the vial
- 5,000 mcg ÷ 2 mL = 2,500 mcg/mL (your concentration)
- 2,500 ÷ 100 = 25 mcg per unit on a U-100 syringe
- 250 mcg ÷ 25 = 10 units to draw
That same vial gives you 20 doses of 250 mcg. Change the water to 1 mL and the dose becomes 5 units; change it to 3 mL and it becomes 15 units — the dose is identical, only the number you draw changes. The dosage guide walks through this step by step, and the peptide dosage chart has ready-made tables by vial size.
How much bacteriostatic water should I add?
More water spreads a small dose across more units, which makes tiny amounts easier to measure accurately; less water concentrates it into fewer units. Neither changes how much peptide is in each dose — only the reading on the barrel. A good rule of thumb is to pick a water amount that puts your usual dose at a round, easy-to-read number of units (say 10–50), so you’re never squinting between the marks. The calculator’s “Help me pick water” mode works this out for you automatically.
Reading units on a U-100 insulin syringe
Peptides are drawn with a U-100 insulin syringe, where 100 units equals 1 mL, so each unit is 0.01 mL. The 0.3 mL (30-unit) and 0.5 mL (50-unit) barrels are marked every single unit, which makes small draws easier to read than the 1 mL (100-unit) barrel, which is marked every two units. “Units” are a volume on the barrel — not a fixed amount of peptide — so how much peptide sits in each unit depends entirely on your concentration. See the glossary for the terms.
Single peptide or a blend
For one peptide in a vial, use the single calculator above. If you’ve combined multiple peptides in one vial (a blend) and want to know how much of each is in a given draw, switch to the blend mode or open the full peptide blend calculator. Either way, you can save any calculation to your free account and build a dosing calendar with reminders so you never miss a dose.
This peptide calculator is an educational math tool only and is not medical advice. Always follow the guidance of a qualified healthcare provider and your product’s labeling.
Reconstitution & dosing FAQ
How do I convert mg to mcg (and mcg to mg)?
1 milligram (mg) equals 1,000 micrograms (mcg). To go from mg to mcg, multiply by 1,000; to go from mcg to mg, divide by 1,000. For example, a 250 mcg dose is 0.25 mg, and a 5 mg vial holds 5,000 mcg. Most peptide vials are labeled in mg while doses are given in mcg, so this is the first conversion most people need.
How do I read insulin syringe unit lines?
A U-100 insulin syringe measures 100 units per 1 mL, so each unit equals 0.01 mL. "U-100" is the scale, not the barrel size — the common barrels are all U-100 and just differ in capacity: a 1 mL barrel is marked up to 100 units, a 0.5 mL barrel up to 50 units, and a 0.3 mL barrel up to 30 units. (There is no separate "U-50" syringe — a 0.5 mL barrel is simply a 50-unit U-100 syringe.) The smaller, finer-marked barrels make small draws easier to read. Note that "units" here are volume marks on the barrel, not a fixed amount of peptide — how much peptide is in each unit depends on your concentration.
How many units should I draw for my dose?
Units to draw = dose (in mcg) ÷ micrograms per unit. Micrograms per unit = (vial mg × 1,000) ÷ (water mL × 100). Enter your vial size, water, and dose above and the calculator does this automatically, then shows the exact fill line on a syringe.
Does adding more or less bacteriostatic water change my dose?
No. The volume of bacteriostatic water only changes the concentration — and therefore how many units you draw — not the actual amount of peptide in each dose. More water means you draw more units for the same dose (easier to measure small doses); less water means fewer units.
What is bacteriostatic water and why is it used?
Bacteriostatic water is sterile water containing 0.9% benzyl alcohol, which inhibits bacterial growth so a reconstituted multi-dose vial stays usable for longer (commonly up to ~28 days refrigerated). It is the standard diluent for reconstituting lyophilized (freeze-dried) peptides.
How many doses does one vial hold?
Doses per vial = total vial amount ÷ dose per injection, in the same units. For example, a 5 mg (5,000 mcg) vial at a 250 mcg dose gives 20 doses. The calculator shows this as "doses per vial" so you can plan how long a vial lasts.