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 the math works
Concentration = peptide (mg) ÷ bacteriostatic water (mL). Your target dose is converted to micrograms, then divided by the concentration to get the injection volume. On a U-100 syringe, 100 units = 1 mL, so we multiply the volume by 100 to give you units.
This tool is for educational purposes only and is not medical advice. Always follow the guidance of a qualified healthcare professional.
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.