By Tessaro Pty Ltd, the maker of Pepti · Reviewed
Enter what is on your vial, how much water you added, and the dose you already have. The calculator converts that into a draw volume, U-100 syringe units, and how many doses the vial holds. It works the same for BPC-157, semaglutide, tirzepatide, or any lyophilised peptide.
This free calculator works out the exact volume to draw and the U-100 syringe units for your peptide — straight from your vial size, the amount of water you mixed in, and the dose you already have.
It is a measurement tool that never suggests a dose: you tell it the dose you already have, and it does the arithmetic. For the working explained step by step, read how to work out what to draw; when you want it in your pocket, get Pepti.
Fill in all three values to see your draw.
Concentration (mg/mL) = vial strength (mg) ÷ water added (mL) Volume to draw (mL) = your dose (mg) ÷ concentration (mg/mL) Syringe units = volume (mL) × 100 (U-100 syringe) Doses per vial = water added (mL) ÷ volume per dose (mL)
Most insulin syringes sold for at-home use are U-100, marked 0 to 100 units. If your syringe is marked in units and reaches 100, the units figure applies. If it is marked in millilitres only, read the mL figure directly. The full working is on the reconstitution guide.
A 10 mg vial with 2 mL of bacteriostatic water added gives 5 mg/mL. A 0.5 mg target means 0.5 ÷ 5 = 0.1 mL. 0.1 mL × 100 = 10 units on a U-100 syringe. 2 mL of water, drawing 0.1 mL per dose, gives 20 doses.
If you change how much water you add, every unit number you had memorised is wrong. The vial has not changed — the concentration has. Run the numbers again from the top whenever your water volume changes, and write the new figure on the vial.
This tool converts values you already have. It does not recommend, suggest, or calculate any dose.
If you would rather not do this by hand every time, the Pepti peptide tracker does the maths and tracks what is left in each vial.
Not medical advice. Pepti is a record-keeping and measurement tool, not a medical device.
Get Pepti on the App Store